I85PREP
⌘ K
Public Nutritionist (China) - independent subject foundations study materials
Public Nutritionist (China) - independent subject foundations study resources

Public Nutritionist (China) - independent subject foundations practice questions

One question at a time. Build your Public Nutritionist (China) - independent subject foundations understanding.

First 50 of 190 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Nutrients, digestion and metabolic reasoning

Which option correctly lists the nine amino acids considered essential for adult humans?

  1. Lysine, Tryptophan, Phenylalanine, Methionine, Threonine, Isoleucine, Leucine, Valine, and Histidine Correct answer.
  2. Lysine, Arginine, Histidine, Methionine, Threonine, Isoleucine, Leucine, and Valine
  3. Tryptophan, Phenylalanine, Tyrosine, Cysteine, Threonine, Leucine, Isoleucine, and Valine
  4. Glutamine, Asparagine, Proline, Glycine, Alanine, Serine, Glutamate, and Aspartate

Explanation

The nine amino acids considered essential in adults are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The older teaching that lists only eight adult essential amino acids and reserves histidine for infants is outdated.

Question 2Nutrients, digestion and metabolic reasoning

In nutritional protein quality evaluation, which amino acid is recognized as the primary First Limiting Amino Acid (第一限制氨基酸) in common cereal grains (谷类蛋白质) such as wheat and rice?

  1. Methionine (甲硫氨酸)
  2. Tryptophan (色氨酸)
  3. Lysine (赖氨酸) Correct answer.
  4. Threonine (苏氨酸)

Explanation

Cereal proteins (wheat, rice, corn) are characteristically deficient in Lysine (赖氨酸), which serves as their first limiting amino acid. Combining cereals with legumes (大豆/豆类, which are rich in lysine but limited in methionine) produces protein complementary effects (蛋白质互补作用), substantially improving the overall Protein Digestibility-Corrected Amino Acid Score (PDCAAS).

Question 3Nutrients, digestion and metabolic reasoning

Which of the following pairs represents the two strictly Essential Fatty Acids (必需脂肪酸) that must be obtained directly from the diet in humans?

  1. Linoleic Acid (亚油酸, n-6) and Alpha-Linolenic Acid (α-亚麻酸, n-3) Correct answer.
  2. Oleic Acid (油酸, n-9) and Palmitic Acid (棕榈酸)
  3. Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA)
  4. Arachidonic Acid (花生四烯酸) and Stearic Acid (硬脂酸)

Explanation

Humans lack the delta-12 and delta-15 desaturase enzymes required to insert double bonds beyond carbon-9 from the carboxyl end. Therefore, Linoleic Acid (18:2 n-6 / 亚油酸) and Alpha-Linolenic Acid (18:3 n-3 / α-亚麻酸) are the only two strictly essential fatty acids. EPA, DHA, and Arachidonic acid can be synthesized endogenously from these parent essential fatty acids, though conversion efficiency may be limited.

Question 4Nutrients, digestion and metabolic reasoning

In human lipoprotein metabolism, which apolipoprotein serves as the primary structural protein and ligand for LDL receptors, directly mediating Low-Density Lipoprotein (LDL / 低密度脂蛋白) cellular uptake?

  1. Apolipoprotein A-I (ApoA-I)
  2. Apolipoprotein C-II (ApoC-II)
  3. Apolipoprotein B-100 (ApoB-100 / 载脂蛋白B-100) Correct answer.
  4. Apolipoprotein E (ApoE)

Explanation

Apolipoprotein B-100 (ApoB-100) is synthesized in the liver and is the primary structural protein of VLDL, IDL, and LDL. ApoB-100 acts as the specific ligand that binds to the LDL receptor (ApoB/E receptor) on peripheral cells and hepatocytes to mediate receptor-mediated endocytosis of atherogenic LDL particles.

Question 5Nutrients, digestion and metabolic reasoning

A food portion contains 30 g of available carbohydrates and has a Glycemic Index (GI / 血糖生成指数) of 80. What is the Glycemic Load (GL / 血糖负荷) of this food portion, and how is it classified?

  1. GL = 24 (High Glycemic Load / 高血糖负荷) Correct answer.
  2. GL = 240 (High Glycemic Load)
  3. GL = 12 (Medium Glycemic Load / 中血糖负荷)
  4. GL = 2.4 (Low Glycemic Load / 低血糖负荷)

Explanation

Glycemic Load (GL) is calculated using the formula: GL = (GI × Available Carbohydrates in grams) / 100. Here, GL = (80 × 30) / 100 = 24. A GL value ≥20 is classified as High GL (高血糖负荷), 11–19 is Medium GL, and ≤10 is Low GL.

Question 6Nutrients, digestion and metabolic reasoning

Which of the three major macronutrients possesses the highest Thermic Effect of Food (TEF / 食物热效应, also known as Specific Dynamic Action SDA), accounting for approximately 20%–30% of its ingested caloric value?

  1. Carbohydrates (碳水化合物)
  2. Fats / Lipids (脂肪)
  3. Protein (蛋白质) Correct answer.
  4. Dietary Fiber (膳食纤维)

Explanation

Thermic Effect of Food (TEF / 食物热效应) represents the energetic cost of digesting, absorbing, metabolizing, and storing nutrients. Protein has by far the highest TEF (20%–30% of energy content), primarily due to the energy costs of peptide hydrolysis, urea synthesis, and protein turnover. In contrast, carbohydrates have a TEF of 5%–10% and fats have a TEF of 0%–5%.

Question 7Nutrients, digestion and metabolic reasoning

A clinical patient presents with impaired dark adaptation (夜盲症), conjunctival xerosis, and triangular foamy white patches on the bulbar conjunctiva known as Bitot's spots (毕脱斑). This clinical presentation is classic for a deficiency of which vitamin?

  1. Vitamin A (Retinol / 维生素A) Correct answer.
  2. Vitamin D (Calciferol / 维生素D)
  3. Vitamin B2 (Riboflavin / 维生素B2)
  4. Vitamin C (Ascorbic Acid / 维生素C)

Explanation

Vitamin A (Retinol) is essential for the regeneration of rhodopsin (视紫红质) in retinal rod cells for dark adaptation and for maintaining normal differentiation of epithelial tissues. Severe Vitamin A deficiency causes nyctalopia (夜盲症), xerophthalmia (干眼病), corneal ulceration/keratomalacia, and Bitot's spots (毕脱斑 - localized keratinized squamous metaplasia on the bulbar conjunctiva).

Question 8Nutrients, digestion and metabolic reasoning

Which enzyme in the proximal renal tubules catalyzes the final and critical activation step of Vitamin D, converting 25-hydroxyvitamin D3 [25(OH)D3] into the biologically active hormonal form 1,25-dihydroxyvitamin D3 [1,25(OH)2D3 / 骨化三醇]?

  1. 25-Hydroxylase (25-羟化酶 / CYP2R1)
  2. 1α-Hydroxylase (1α-羟化酶 / CYP27B1) Correct answer.
  3. 24-Hydroxylase (24-羟化酶 / CYP24A1)
  4. 7-Dehydrocholesterol reductase

Explanation

Endogenous Vitamin D3 synthesized in the skin or absorbed from the diet is first hydroxylated in the liver by 25-hydroxylase (CYP2R1) into 25(OH)D3 (the main circulating storage form). In the kidneys, the enzyme 1α-hydroxylase (CYP27B1), located in the proximal renal tubular cells and tightly regulated by PTH, converts 25(OH)D3 into 1,25(OH)2D3 (Calcitriol / 骨化三醇), the active endocrine hormone.

Question 9Nutrients, digestion and metabolic reasoning

What is the primary physiological mechanism by which Vitamin E (Alpha-tocopherol / α-生育酚) protects cellular membranes against oxidative damage?

  1. Serving as a co-factor for the microsomal cytochrome P450 monooxygenase system
  2. Directly reducing oxidized glutathione (GSSG) back to reduced glutathione (GSH)
  3. Acting as a lipid-soluble chain-breaking antioxidant that scavenges lipid peroxyl radicals in polyunsaturated fatty acid membranes (终止多不饱和脂肪酸脂质过氧化链式反应) Correct answer.
  4. Chelating extracellular divalent calcium and iron ions in the vascular lumen

Explanation

Vitamin E (α-tocopherol) resides inside the hydrophobic core of cellular phospholipid membranes and plasma lipoproteins. It acts as the primary fat-soluble chain-breaking antioxidant, donating its phenolic hydrogen atom to lipid peroxyl radicals (LOO• -> LOOH), thereby arresting the propagation of lipid peroxidation chain reactions in membrane Polyunsaturated Fatty Acids (PUFAs).

Question 10Nutrients, digestion and metabolic reasoning

Vitamin K acts as an essential coenzyme for gamma-glutamyl carboxylase (γ-谷氨酰羧化酶), which carboxylates glutamic acid residues to form functional calcium-binding Gla domains. Which of the following sets of blood coagulation factors is strictly Vitamin K-dependent?

  1. Factors I (Fibrinogen), V, VIII, and XIII
  2. Factors XI, XII, Prekallikrein, and High-Molecular-Weight Kininogen
  3. Factors III (Tissue Factor), IV (Calcium), and Von Willebrand Factor
  4. Factors II, VII, IX, and X, along with Proteins C and S (凝血因子 II、VII、IX、X 及蛋白C、蛋白S) Correct answer.

Explanation

Vitamin K is the necessary co-factor for the post-translational γ-carboxylation of specific glutamic acid (Glu) residues into γ-carboxyglutamic acid (Gla) on blood coagulation Factors II (Prothrombin), VII, IX, and X, as well as endogenous anticoagulants Protein C and Protein S. This carboxylation enables these proteins to bind calcium ions and adhere to negatively charged platelet phospholipid surfaces. Warfarin functions by antagonizing Vitamin K epoxide reductase (VKOR).

Question 11Nutrients, digestion and metabolic reasoning

A patient presents with bilateral angular cheilitis (口角炎), magenta-colored swollen tongue (舌炎), cheilosis (唇炎), and seborrheic scrotal dermatitis (阴囊炎). This classic 'oral-ocular-genital' clinical syndrome is characteristic of a deficiency of:

  1. Vitamin B1 (Thiamine / 硫胺素)
  2. Vitamin B2 (Riboflavin / 核黄素) Correct answer.
  3. Folic Acid (叶酸)
  4. Vitamin E (生育酚)

Explanation

Vitamin B2 (Riboflavin) serves as the structural component of coenzymes FMN (Flavin Mononucleotide) and FAD (Flavin Adenine Dinucleotide) involved in biological oxidation-reduction reactions. Riboflavin deficiency classically manifests as the 'oral-ocular-genital syndrome' characterized by angular stomatitis/cheilitis (口角炎), glossitis (舌炎 / 地图舌 / 杨梅舌), cheilosis (唇裂), corneal vascularization, and scrotal/vulvar dermatitis (阴囊炎).

Question 12Nutrients, digestion and metabolic reasoning

In human metabolic pathways, approximately how many milligrams of dietary Tryptophan (色氨酸) are required to biosynthesize 1 mg of Niacin (烟酸 / 维生素B3)?

  1. 10 mg
  2. 100 mg
  3. 60 mg (60 mg 色氨酸 = 1 mg 烟酸当量 NE) Correct answer.
  4. 600 mg

Explanation

In human liver metabolism, dietary tryptophan is converted into niacin via the kynurenine pathway (requiring Vitamin B6, B2, and iron as co-factors). On average, 60 mg of dietary tryptophan yields 1 mg of niacin. Total Niacin Equivalents (NE / 烟酸当量) are calculated as: Niacin Equivalents (mg NE) = Dietary Niacin (mg) + [Dietary Tryptophan (mg) / 60].

Question 13Nutrients, digestion and metabolic reasoning

Vitamin C (Ascorbic Acid / 抗坏血酸) facilitates intestinal absorption of dietary Non-Heme Iron (非血红素铁) primarily by:

  1. Stimulating the synthesis of transferrin in the enterocyte cytoplasm
  2. Reducing insoluble ferric iron (Fe3+) to soluble ferrous iron (Fe2+) and forming absorbable iron-ascorbate chelates (将三价铁还原为易吸收的二价铁并形成可溶性螯合物) Correct answer.
  3. Inhibiting the basolateral ferroportin export channel in intestinal enterocytes
  4. Degrading systemic hepcidin in hepatic sinusoids

Explanation

Dietary non-heme iron exists predominantly in the insoluble ferric form (Fe3+). Vitamin C is a powerful reducing agent that donates electrons in the gastric and duodenal lumen to reduce Fe3+ to the soluble, absorbable ferrous state (Fe2+), while also forming stable soluble iron-chelate complexes at neutral duodenal pH, significantly increasing divalent metal transporter 1 (DMT1) uptake.

Question 14Nutrients, digestion and metabolic reasoning

Which of the following dietary iron sources is classified as Heme Iron (血红素铁), exhibiting high bioavailability (15%–35%) that is minimally inhibited by dietary phytates, polyphenols, or oxalates?

  1. Iron in spinach, legumes, and whole wheat grains
  2. Ferrous sulfate added to fortified breakfast cereals
  3. Iron contained in hemoglobin and myoglobin of red meat, animal liver, and blood curd (瘦肉、动物肝脏、动物血中的血红蛋白与肌红蛋白铁) Correct answer.
  4. Iron in egg yolk bound to phosvitin

Explanation

Heme iron (血红素铁) exists as iron porphyrin complexes in animal hemoglobin and myoglobin (red meat, poultry, fish, animal liver, blood curd). It is absorbed intact via heme carrier protein 1 (HCP1) with high bioavailability (15%–35%) and is virtually unaffected by dietary inhibitors like phytates, tannins, or oxalates. In contrast, non-heme iron (plant foods, egg yolk, dairy, supplements) has low bioavailability (2%–10%) and is strongly inhibited by phytates and polyphenols.

Question 15Nutrients, digestion and metabolic reasoning

A pediatric patient with severe chronic diarrhea and total parenteral nutrition unsupplemented with trace elements develops perioral and perianal vesiculobullous dermatitis, alopecia, and failure to thrive. This presentation, mimicking Acrodermatitis Enteropathica (肠病性肢端皮炎), is caused by a severe deficiency of:

  1. Selenium (硒)
  2. Copper (铜)
  3. Manganese (锰)
  4. Zinc (锌) Correct answer.

Explanation

Zinc is an indispensable trace element acting as a catalytic or structural component for over 300 metalloenzymes (DNA/RNA polymerases, alkaline phosphatase, carbonic anhydrase) and zinc-finger transcription factors. Severe zinc deficiency causes Acrodermatitis Enteropathica (肠病性肢端皮炎), characterized by periorificial and acral pustular dermatitis, alopecia, intractable diarrhea, impaired wound healing, and immune dysfunction.

Question 16Nutrients, digestion and metabolic reasoning

Glutathione Peroxidase (GPx / 谷胱甘肽过氧化物酶), a critical antioxidant enzyme that reduces lipid hydroperoxides to alcohols and hydrogen peroxide to water, incorporates which essential trace element in the form of selenocysteine (硒代半胱氨酸)?

  1. Selenium (硒) Correct answer.
  2. Molybdenum (钼)
  3. Chromium (铬)
  4. Iodine (碘)

Explanation

Selenium (硒) is an essential trace element incorporated as the 21st amino acid, Selenocysteine (Sec / 硒代半胱氨酸), into selenoproteins including Glutathione Peroxidase (GPx-1 to GPx-6), Thioredoxin Reductase (TrxR), and Iodothyronine Deiodinases (DIO1, DIO2). GPx utilizes reduced glutathione to neutralize intracellular peroxides, protecting biomembranes from oxidative destruction.

Question 17Dietary assessment and interpretable nutrition data

A hospitalized adult patient consumes 75 g of dietary protein in 24 hours. The 24-hour urine collection shows a Urinary Urea Nitrogen (UUN / 尿尿素氮) of 8 g. Assuming standard unmeasured skin and fecal nitrogen losses (4 g/day), what is the patient's Nitrogen Balance (氮平衡)?

  1. +4 g (Positive nitrogen balance)
  2. 0 g (Neutral nitrogen balance / 零氮平衡) Correct answer.
  3. -4 g (Negative nitrogen balance)
  4. +12 g (Positive nitrogen balance)

Explanation

Nitrogen Balance (g) = Nitrogen Intake - Nitrogen Output. Nitrogen Intake = Protein intake (g) / 6.25 = 75 / 6.25 = 12 g N. Nitrogen Output = UUN (g) + 4 g (fecal, skin, and non-urea urinary nitrogen losses) = 8 + 4 = 12 g N. Nitrogen Balance = 12 g - 12 g = 0 g, indicating a neutral nitrogen balance (零氮平衡).

Question 18Dietary assessment and interpretable nutrition data

Under the Chinese Dietary Reference Intakes (DRIs / 中国居民膳食营养素参考摄入量), which metric is defined as the daily nutrient intake level estimated to meet the physiological requirements of 97%–98% of healthy individuals in a specific life stage and sex group?

  1. Estimated Average Requirement (EAR / 平均需要量)
  2. Adequate Intake (AI / 适宜摄入量)
  3. Tolerable Upper Intake Level (UL / 可耐受最高摄入量)
  4. Recommended Nutrient Intake (RNI / 推荐摄入量) Correct answer.

Explanation

Under the Chinese DRIs framework: EAR (平均需要量) meets the needs of 50% of the population. Recommended Nutrient Intake (RNI = EAR + 2 SD) is set to meet the daily requirements of 97%–98% of healthy individuals. Adequate Intake (AI) is used when EAR cannot be determined. Tolerable Upper Intake Level (UL) is the maximum safe daily intake unlikely to pose health risks.

Question 19Dietary assessment and interpretable nutrition data

According to the Chinese Guidelines for the Prevention and Control of Overweight and Obesity in Adults (中国成人超重和肥胖症预防控制指南), Central / Abdominal Obesity (中心性肥胖 / 腹型肥胖) is defined by which Waist Circumference (腰围 WC) cutoffs in Chinese adults?

  1. Men ≥90 cm, Women ≥85 cm (男性 ≥90 cm，女性 ≥85 cm) Correct answer.
  2. Men ≥102 cm, Women ≥88 cm
  3. Men ≥85 cm, Women ≥80 cm
  4. Men ≥95 cm, Women ≥90 cm

Explanation

In Chinese adults, ethnic-specific criteria established by the National Health Commission define central (abdominal) obesity as a Waist Circumference (WC) ≥90 cm for men and ≥85 cm for women. This reflects the increased visceral adipose accumulation and heightened cardiometabolic risk at lower absolute thresholds compared to Western populations (where cutoffs are often 102 cm for men and 88 cm for women).

Question 20Dietary assessment and interpretable nutrition data

In the Nutritional Risk Screening 2002 (NRS 2002 / 营养风险筛查 2002) tool recommended by CSPEN and ESPEN for hospitalized patients, what is the cutoff total score indicating that a patient is at Nutritional Risk (存在营养风险) and requires an individualized nutritional support care plan?

  1. Total Score ≥1 point
  2. Total Score ≥5 points
  3. Total Score ≥3 points (总分 ≥3 分) Correct answer.
  4. Total Score = 0 points

Explanation

NRS 2002 comprises three components: 1) Impaired Nutritional Status score (0–3 points based on weight loss, BMI, and dietary intake reduction); 2) Severity of Disease score (0–3 points based on metabolic stress); and 3) Age adjustment (1 point for age ≥70 years). A Total Score ≥3 points indicates 'nutritional risk' (存在营养风险), mandating the formulation and execution of a clinical nutrition intervention plan.

Question 21Dietary assessment and interpretable nutrition data

The Mini Nutritional Assessment Short-Form (MNA-SF / 微型营养评估简表) is an internationally validated screening tool specifically designed and recommended for which patient population?

  1. Neonates and infants in the NICU
  2. Pregnant women in their first trimester
  3. Elite competitive athletic trainees
  4. Geriatric elderly individuals (age ≥65 years) in hospital, nursing home, and community settings (≥65岁老年人群) Correct answer.

Explanation

The Mini Nutritional Assessment (MNA) and MNA-SF (6 questions, total 14 points: 12–14 normal, 8–11 at risk of malnutrition, 0–7 malnourished) are specifically validated and calibrated for Geriatric populations (age ≥65 years). It assesses appetite, weight loss, mobility, acute psychological stress, neuropsychological problems (dementia/depression), and BMI or calf circumference.

Question 22Dietary assessment and interpretable nutrition data

In the Subjective Global Assessment (SGA / 主观全面评定) framework for clinical nutritional status, what are the three categorical diagnostic grades assigned to patients based on medical history and physical examination?

  1. SGA-A: Well Nourished; SGA-B: Moderately Malnourished (or suspected); SGA-C: Severely Malnourished (SGA-A 良好；SGA-B 中度营养不良；SGA-C 重度营养不良) Correct answer.
  2. Grade 1: Overweight; Grade 2: Obese; Grade 3: Morbidly Obese
  3. Stage I: Pre-diabetes; Stage II: Diabetes; Stage III: End-stage
  4. Level 0: Safe; Level 1: Low Risk; Level 2: High Risk

Explanation

Subjective Global Assessment (SGA) integrates medical history (weight changes in past 6 months, dietary intake change, gastrointestinal symptoms >2 weeks, functional capacity) and bedside physical examination (loss of subcutaneous fat, muscle wasting, ankle/sacral edema, ascites). Patients are qualitatively categorized into: SGA-A (Well Nourished / 营养良好), SGA-B (Moderately Malnourished / 中度营养不良), or SGA-C (Severely Malnourished / 重度营养不良).

Question 23Dietary assessment and interpretable nutrition data

In anthropometric nutritional assessment, Mid-Arm Muscle Circumference (MAMC / 上臂肌围) is calculated using Mid-Upper Arm Circumference (MUAC / AC) and Triceps Skinfold thickness (TSF / S) via the formula: MAMC (cm) = MUAC (cm) - [π × TSF (cm)]. What specific anatomical body compartment does MAMC primarily reflect?

  1. Subcutaneous adipose fat stores only
  2. Somatic skeletal muscle protein mass and lean tissue reserves (机体骨骼肌蛋白质储备与瘦体重) Correct answer.
  3. Total bone mineral density and skeleton weight
  4. Total extracellular fluid volume in the vascular space

Explanation

While Triceps Skinfold (TSF / 三头肌皮褶厚度) measures subcutaneous adipose fat stores, Mid-Arm Muscle Circumference (MAMC / 上臂肌围) subtracts the skinfold fat layer from the total arm circumference to estimate the cross-sectional muscle area of the arm, serving as an index of somatic skeletal muscle protein mass and lean tissue reserves.

Question 24Dietary assessment and interpretable nutrition data

Which of the following describes the diagnostic framework of the Global Leadership Initiative on Malnutrition (GLIM / 全球营养不良领导倡议) consensus criteria for diagnosing adult malnutrition?

  1. Diagnosing malnutrition based exclusively on serum cholesterol <3.0 mmol/L without any physical exam
  2. Diagnosing malnutrition only if the patient has lost >50% body weight in 24 hours
  3. A single-step approach using urine color charts alone
  4. A two-step approach: First screen for nutritional risk with a validated tool (e.g., NRS 2002); then confirm diagnosis by meeting at least ONE Phenotypic criterion (weight loss, low BMI, reduced muscle mass) AND at least ONE Etiologic criterion (reduced food intake/assimilation, disease burden/inflammation) (两步法：先用NRS 2002等筛查风险；诊断需满足至少1项表型标准及至少1项病因标准) Correct answer.

Explanation

The GLIM consensus criteria establish a unified global 2-step diagnostic model: Step 1: Identify 'at risk' status using validated screening tools (e.g., NRS 2002, MUST, MNA-SF). Step 2: Diagnostic assessment requiring at least 1 Phenotypic Criterion (non-volitional weight loss, low BMI <18.5 or <20 in ≥70y Asians, or reduced muscle mass by BIA/DEXA/anthropometry) AND at least 1 Etiologic Criterion (reduced food intake/assimilation, or disease burden/acute or chronic inflammation).

Question 25Life-course food patterns and practical meal planning

Why do Iron (铁) requirement recommendations increase dramatically during mid-to-late pregnancy (RNI reaching 24–29 mg/day in China DRIs)?

  1. To support maternal blood volume expansion (~40%–50% plasma increase), placental vascular growth, and fetal hepatic iron storage for the first 4–6 months of postnatal life Correct answer.
  2. To stimulate maternal thyroid hormone synthesis in the anterior pituitary
  3. To prevent gestational hypercalcemia and neonatal tetany
  4. To convert excess maternal blood glucose into glycogen

Explanation

During mid-to-late pregnancy, maternal blood volume expands by ~40%–50% (requiring ~500 mg additional elemental iron for erythrocyte hemoglobin mass), placental tissue requires ~100 mg, and the fetus actively accumulates ~300 mg of iron across the placenta into its liver to support hemopoiesis during the first 4–6 months of exclusive breastfeeding when breast milk iron is low.

Question 26Life-course food patterns and practical meal planning

How does Colostrum (初乳, secreted within the first 4–5 days postpartum) differ immunologically and biochemically from mature breast milk (成熟乳)?

  1. Colostrum is richer in Secretory Immunoglobulin A (sIgA), Lactoferrin, white blood cells, and Vitamin A, with lower lactose and fat contents Correct answer.
  2. Colostrum contains exclusively casein proteins with zero immune globulins or minerals
  3. Colostrum has three times higher fat and lactose concentrations than mature milk
  4. Colostrum is acidic and contains toxic waste metabolites that should be expressed and discarded

Explanation

Colostrum (初乳 / secreted days 1–5 postpartum) is a thick, yellowish fluid rich in Secretory Immunoglobulin A (sIgA / 分泌型免疫球蛋白A), Lactoferrin (乳铁蛋白), lysozyme, macrophages, neutrophils, Vitamin A, and zinc, providing passive mucosal immunity to the newborn's sterile gastrointestinal tract. It has higher protein (~22 g/L) and lower fat and lactose than mature milk (成熟乳, which has ~10 g/L protein, higher lactose ~70 g/L, and higher fat ~38 g/L).

Question 27Life-course food patterns and practical meal planning

When introducing Complementary Foods (添加辅食) to an infant reaching 6 months of age, which food item is most strongly recommended as the first introductory solid food to prevent micronutrient deficiency?

  1. Iron-fortified infant rice cereal puree (强化铁的婴儿米粉) or pureed red meat Correct answer.
  2. Whole egg white (纯鸡蛋清)
  3. Unpasteurized whole cow's milk (生鲜牛奶)
  4. Citrus fruit juice with added refined sugar

Explanation

At 6 months of age, the infant's congenital hepatic iron reserves accumulated in utero become depleted while breast milk iron remains low. The first complementary foods (第一口辅食) should be rich in bioavailable iron, smooth in texture, and hypoallergenic-specifically Iron-Fortified Infant Rice Cereal (强化铁的婴儿米粉) mixed with breast milk/water, followed promptly by pureed red meat (beef, pork liver), egg yolk, and vegetable purees.

Question 28Life-course food patterns and practical meal planning

Which of the following foods is strictly contraindicated for infants under 12 months (1 year) of age due to the risk of life-threatening Infant Botulism (婴儿肉毒中毒)?

  1. Natural honey (天然蜂蜜) Correct answer.
  2. Cooked pumpkin puree (煮熟南瓜泥)
  3. Iron-fortified rice cereal (强化铁米粉)
  4. Cooked egg yolk puree (熟蛋黄泥)

Explanation

Natural honey (天然蜂蜜) may contain Clostridium botulinum (肉毒杆菌) endospores. In infants under 1 year, immature intestinal flora and low gastric acidity allow spores to germinate, colonize the colon, and produce botulinum neurotoxin, resulting in Infant Botulism (hypotonia / 'floppy infant syndrome', constipation, cranial nerve palsies, and respiratory arrest). Honey is strictly prohibited under 1 year of age.

Question 29Life-course food patterns and practical meal planning

To prevent choking and airway foreign body aspiration (气管异物窒息) in preschool children aged 3 to 6 years, which type of food should be carefully modified, crushed, or avoided?

  1. Whole hard nuts (peanuts, walnuts), whole small spherical fruits (grapes, cherry tomatoes), and jelly cups Correct answer.
  2. Thoroughly cooked steamed egg custard
  3. Soft mashed potatoes
  4. Cooked soft carrot slices

Explanation

Preschool children have developing molar dentition and immature swallowing coordination. Whole hard nuts (peanuts, almonds), whole spherical smooth foods (grapes, whole cherry tomatoes, longan), hard candies, and gelatinous jelly cups (果冻) pose extreme choking hazards. Nuts should be ground into powders/pastes, and spherical fruits must be quartered lengthwise before serving.

Question 30Life-course food patterns and practical meal planning

Which age-related gastrointestinal physiological change in older adults (≥65 years) frequently leads to malabsorption of dietary Vitamin B12 and non-heme iron?

  1. Atrophic gastritis resulting in reduced gastric acid secretion (胃酸分泌减少 / 胃黏膜萎缩) Correct answer.
  2. Hypersecretion of pancreatic lipase and amylase
  3. Excessive proliferation of terminal ileal microvilli
  4. Accelerated esophageal peristalsis and gastric emptying

Explanation

Atrophic gastritis (萎缩性胃炎) and age-related gastric mucosal atrophy cause hypochlorhydria or achlorhydria (reduced gastric acid). Low gastric acid fails to cleave dietary vitamin B12 from animal food proteins and fails to reduce ferric (Fe3+) iron to ferrous (Fe2+) iron, impairing absorption of both micronutrients. Concurrently, reduced intrinsic factor secretion exacerbates cobalamin deficiency.

Question 31Life-course food patterns and practical meal planning

In the nutritional management of primary Osteoporosis (原发性骨质疏松症) in elderly individuals, what is the synergism between Calcium, Vitamin D, and physical activity?

  1. Vitamin D enhances intestinal calcium absorption and renal reabsorption, while weight-bearing mechanical loading stimulates osteoblast bone formation and piezoelectric mineralization Correct answer.
  2. Calcium directly stimulates cutaneous 7-dehydrocholesterol synthesis during anaerobic exercise
  3. Vitamin D acts solely as a sedative while calcium dissolves bone mineral
  4. Physical activity converts excess bone calcium into vitamin D in skeletal muscle

Explanation

Active 1,25(OH)2D3 upregulates intestinal epithelial TRPV6 calcium channels and calbindin-D9k, boosting calcium absorption efficiency from ~10%–15% to >30%–40%. Concurrently, weight-bearing exercise (walking, tai chi, resistance training) generates mechanical piezoelectric strain in bone tissue, stimulating osteocyte signaling (Wnt/β-catenin pathway) to activate osteoblasts and incorporate absorbed calcium into hydroxyapatite mineral crystals.

Question 32Life-course food patterns and practical meal planning

Individuals who adhere strictly to a 100% Vegan diet (完全素食人群, consuming zero animal flesh, dairy, or eggs) are at the highest risk of clinical deficiency for which vitamin that is found naturally almost exclusively in animal foods?

  1. Vitamin B12 (Cobalamin / 钴胺素) Correct answer.
  2. Vitamin C (Ascorbic acid / 抗坏血酸)
  3. Vitamin E (Alpha-tocopherol / 生育酚)
  4. Vitamin B1 (Thiamine / 硫胺素)

Explanation

Vitamin B12 (Cobalamin / 钴胺素) is synthesized exclusively by bacteria and archaea and is naturally present almost entirely in animal-source foods (meat, liver, fish, eggs, dairy). Strict vegans (完全素食者) consume virtually zero natural dietary B12 and must rely on fortified foods or oral B12 supplements to prevent Megaloblastic Anemia and irreversible subacute combined spinal cord degeneration.

Question 33Life-course food patterns and practical meal planning

Which of the following represents the 8 Core Recommendations (八条准则) of the Dietary Guidelines for Chinese Residents (中国居民膳食指南 2022)?

  1. Food diversity and rational combination; Balance eating and moving for healthy weight; Plenty of vegetables, fruits, dairy, whole grains, and soybeans; Appropriate fish, poultry, eggs, and lean meat; Less salt and oil, control sugar and limit alcohol; Regular meals and adequate hydration; Know how to cook, choose, and read labels; Use serving chopsticks and eliminate waste Correct answer.
  2. High protein, zero carbohydrate; Eliminate all grains; Fast for 20 hours daily; Drink raw animal blood; Avoid all vegetables; Salt food heavily; Dine only in private; Discard leftover food
  3. Eat only fruit during daytime; Drink raw unboiled milk; Consume 100g of cooking oil daily; Avoid exercise; Eat one massive meal before sleep; Never read nutrition labels
  4. Consume equal weights of meat and sugar; Drink 500ml of hard liquor daily; Avoid water; Rely entirely on pharmaceutical vitamin megadoses

Explanation

The 2022 Dietary Guidelines for Chinese Residents (中国居民膳食指南 2022) establish 8 core principles (准则): 1. 一、食物多样，合理搭配; 2. 二、吃动平衡，健康体重; 3. 三、多吃蔬果、奶类、全谷、大豆; 4. 四、适量吃鱼、禽、蛋、瘦肉; 5. 五、少盐少油，控糖限酒; 6. 六、规律进餐，足量饮水; 7. 七、会烹会选，会看标签; 8. 八、公筷分餐，杜绝浪费.

Question 34Life-course food patterns and practical meal planning

Under the 'Food Diversity' (食物多样) guideline of the Dietary Guidelines for Chinese Residents 2022, what is the quantitative target for the average daily and weekly number of different food types consumed by a healthy individual (excluding cooking oils and seasonings)?

  1. At least 12 different food types daily, and at least 25 different food types weekly (平均每天摄入12种以上食物，每周25种以上) Correct answer.
  2. At least 3 different food types daily, and at least 5 different food types weekly
  3. Exactly 50 different food types daily, and 200 weekly
  4. Not more than 5 food types weekly to avoid digestive strain

Explanation

Guideline 1 (Food Diversity, Rational Combination) explicitly specifies that healthy individuals should consume an average of at least 12 different food types per day (每天12种以上) and at least 25 different food types per week (每周25种以上), distributed across 5 major categories: cereals/tubers, vegetables/fruits, animal meats/eggs, milk/soybeans/nuts, and cooking oils/seasonings.

Question 35Life-course food patterns and practical meal planning

In the Chinese Balanced Dietary Pagoda (2022), what are the recommended daily intake quantities for Tier 2 (Vegetables and Fruits / 蔬菜水果类)?

  1. Vegetables: 300–500g (with dark vegetables ≥ 50%); Fruits: 200–350g Correct answer.
  2. Vegetables: 100–150g; Fruits: 50–100g
  3. Vegetables: 800–1000g; Fruits: 800–1000g
  4. Vegetables: 50g; Fruits: 500–800g

Explanation

Tier 2 of the 2022 Chinese Balanced Dietary Pagoda mandates: Fresh Vegetables (蔬菜类) 300–500g per day (ensuring dark vegetables make up over half), and Fresh Fruits (水果类) 200–350g per day. Consuming these amounts provides essential dietary fiber, potassium, magnesium, vitamin C, carotenoids, and protective polyphenols.

Question 36Life-course food patterns and practical meal planning

What update was made to the recommended daily intake of Dairy Products (奶及奶制品) in Tier 4 of the 2022 Chinese Balanced Dietary Pagoda compared to the previous 2016 edition?

  1. Increased from 300g to 300–500g liquid milk equivalent per day (奶及奶制品由300克提高至300–500克) Correct answer.
  2. Decreased from 300g to 100g per day
  3. Maintained strictly at zero due to lactose intolerance prevalence
  4. Increased to 1500g per day

Explanation

In the 2022 revision of the Chinese Balanced Dietary Pagoda, the recommended daily intake of Milk and Dairy Products (奶及奶制品) was formally increased from '300g' (in 2016) to '300–500g' liquid milk equivalent per day (alongside 25–35g of Soybeans and Nuts / 大豆和坚果类), in order to address widespread chronic calcium deficiency in the Chinese population.

Question 37Life-course food patterns and practical meal planning

What are the strict daily quantitative limits set for Salt (食盐) and Cooking Oil (烹调油) at the pinnacle (Tier 5) of the 2022 Chinese Balanced Dietary Pagoda?

  1. Salt: < 5g per day (reduced from < 6g); Cooking Oil: 25–30g per day Correct answer.
  2. Salt: < 12g per day; Cooking Oil: 50–60g per day
  3. Salt: < 1g per day; Cooking Oil: 0g per day
  4. Salt: < 10g per day; Cooking Oil: 10–15g per day

Explanation

Tier 5 (Pinnacle / 塔顶) of the 2022 Pagoda establishes strict upper limits: Salt (食盐) is tightened from <6g/day down to < 5g per day (< 2000 mg sodium) to align with WHO hypertension reduction targets. Cooking Oil (烹调油) is maintained at 25–30g per day (favoring plant oils with varied fatty acid profiles). Added sugars should also be controlled to < 50g/day (preferably < 25g/day).

Question 38Life-course food patterns and practical meal planning

When designing a balanced daily meal plan for a standard working adult, what is the standard recommended energy distribution ratio across Breakfast, Lunch, and Dinner (三餐能量分配比例)?

  1. Breakfast: 25%–30%; Lunch: 30%–40%; Dinner: 30%–35% (standard 3 : 4 : 3 proportion) Correct answer.
  2. Breakfast: 5%; Lunch: 15%; Dinner: 80%
  3. Breakfast: 50%; Lunch: 50%; Dinner: 0%
  4. Breakfast: 10%; Lunch: 80%; Dinner: 10%

Explanation

Standard Chinese nutritional recipe design principles mandate a balanced 3-meal energy allocation of approximately 3:4:3 (Breakfast: 25%–30%, Lunch: 30%–40%, Dinner: 30%–35%). This ensures adequate morning cognitive and physical energy, optimal midday replenishment, and prevents heavy late-night dinners that disrupt circadian metabolic regulation and promote adiposity.

Question 39Food-service systems, contamination and quality control

A hospital catering outbreak of acute food poisoning occurs within 1–6 hours after consuming cream pastries and cooked meats, presenting with severe projectile vomiting, abdominal cramps, and subnormal body temperature without fever. Which pathogen and toxin is responsible?

  1. Salmonella enterica invasive infection
  2. Clostridium botulinum neurotoxin
  3. Staphylococcus aureus preformed heat-stable enterotoxin (金黄色葡萄球菌产生的耐热性肠毒素) Correct answer.
  4. Vibrio parahaemolyticus thermostable direct hemolysin

Explanation

Staphylococcus aureus food poisoning is an intoxication caused by ingesting preformed, heat-stable staphylococcal enterotoxins (types A–E, which withstand 100°C boiling for 30 minutes) in contaminated dairy, cream pastries, or cooked meats. It features an exceptionally short incubation period (1–6 hours, average 2–4 hours) characterized by explosive nausea, projectile vomiting, and abdominal cramps, typically without fever.

Question 40Food-service systems, contamination and quality control

Which of the following foodborne bacterial pathogens is Halophilic (嗜盐性, requiring 2%–4% NaCl for optimal growth) and is the most common cause of bacterial food poisoning associated with raw or undercooked marine seafood (海产品) in coastal regions of China?

  1. Vibrio parahaemolyticus (副溶血性弧菌) Correct answer.
  2. Campylobacter jejuni
  3. Listeria monocytogenes
  4. Shigella dysenteriae

Explanation

Vibrio parahaemolyticus (副溶血性弧菌) is a Gram-negative, halophilic (嗜盐) bacterium naturally inhabiting marine coastal environments. It requires 2%–4% sodium chloride to thrive. Ingestion of raw, contaminated, or cross-contaminated marine seafood (fish, shrimp, crabs, shellfish, salted jellyfish) causes acute gastroenteritis characterized by watery/bloody diarrhea, abdominal colic, and fever within 12–24 hours.

Question 41Food-service systems, contamination and quality control

Aflatoxin B1 (黄曲霉毒素 B1), produced by Aspergillus flavus and Aspergillus parasiticus in moldy peanuts, corn, and tree nuts, is classified by IARC as a Group 1 human carcinogen. Which organ is its primary target for inducing malignant transformation via p53 gene transversion mutations?

  1. Brain (Glioblastoma)
  2. Liver (Hepatocellular Carcinoma / 原发性肝细胞癌) Correct answer.
  3. Skin (Basal Cell Carcinoma)
  4. Thyroid (Papillary Carcinoma)

Explanation

Aflatoxin B1 (AFB1) is metabolized by hepatic cytochrome P450 enzymes into AFB1-8,9-epoxide, which covalently binds to DNA, inducing specific G->T transversion mutations at codon 249 of the TP53 tumor suppressor gene. It is one of the most potent hepatocarcinogens known, acting synergistically with chronic Hepatitis B (HBV) infection to cause Hepatocellular Carcinoma (HCC / 原发性肝癌). AFB1 is extremely heat-stable (decomposition temperature ~268°C).

Question 42Population prevention, screening and health communication

What is the primary public health objective of universal salt iodization (加碘食盐 GB 26878) implemented throughout China?

  1. Preventing Iodine Deficiency Disorders (IDD / 碘缺乏病), including Endemic Goiter and Cretinism Correct answer.
  2. Preventing Keshan disease and Kashin-Beck osteoarthropathy
  3. Accelerating gastric hydrochloric acid production to prevent pernicious anemia
  4. Enhancing the preservative osmotic pressure of table salt

Explanation

China's mandatory Universal Salt Iodization (USI / 食盐加碘) program, standardized under GB 26878 (potassium iodate KIO3 concentration ~18–30 mg/kg), was implemented to eradicate Iodine Deficiency Disorders (IDD / 碘缺乏病), including endemic goiter (地方性甲状腺肿), endemic cretinism (克汀病 / 呆小病), and fetal neurological developmental impairments across iodine-deficient ecological regions.

Question 43Population prevention, screening and health communication

What is the recommended baseline physical activity level for healthy adults in the Dietary Guidelines for Chinese Residents 2022 to maintain energy balance and a healthy body weight?

  1. At least 150 minutes of moderate-intensity aerobic exercise per week (or equivalent to at least 6,000 steps of brisk walking per day), with muscle-strengthening activities 2–3 days per week Correct answer.
  2. At least 60 minutes of maximal-intensity sprint intervals every 2 hours without rest
  3. Strict physical inactivity and bed rest
  4. Exactly 500 steps per week

Explanation

Guideline 2 (Eat-Move Balance, Healthy Weight / 吃动平衡，健康体重) recommends that healthy adults engage in at least 150 minutes of moderate-intensity aerobic activity per week (or 75 minutes of vigorous activity), distributed over at least 5 days, or accumulate active movement equivalent to at least 6,000 steps (6000步) of brisk walking daily, alongside resistance muscle training 2–3 days per week while minimizing sedentary screen time.

Question 44Population prevention, screening and health communication

What is the primary objective of Community Nutrition Surveillance (社区营养监测 / 营养监测) within national public health systems?

  1. Continuously and systematically collecting, analyzing, and interpreting population nutritional status, dietary intake, and socioeconomic factors to formulate, guide, and evaluate public nutrition policies and interventions Correct answer.
  2. Physically inspecting every individual citizen's kitchen refrigerator daily
  3. Banning the commercial sale of all grain products
  4. Distributing prescription pharmaceutical drugs in community supermarkets

Explanation

Community Nutrition Surveillance (营养监测 / Nutrition Surveillance, as defined by WHO/FAO and implemented in China's National Nutrition and Health Survey / 中国居民营养与健康状况监测) involves the continuous, systematic collection and analysis of population anthropometric, dietary, biochemical, and socioeconomic data to track nutrition trends, identify vulnerable high-risk groups, and provide empirical evidence for policy making (such as the National Nutrition Plan 2017–2030 / 国民营养计划).

Question 45Population prevention, screening and health communication

In community nutrition education and behavioral counseling, according to the Transtheoretical Model (TTM / 跨理论模型 / 行为改变阶段理论), what is the appropriate educational strategy for an individual in the 'Precontemplation Stage' (前意向阶段 / 无准备阶段)?

  1. Raise awareness of health risks and the personal benefits of change through gentle consciousness-raising information, without pressuring immediate action Correct answer.
  2. Demand that the client immediately discard all food in their pantry and begin a strict diet tomorrow
  3. Teach advanced recipe nutrient calculation formulas and meal prep routines
  4. Reward the client for maintaining a 6-month continuous behavior change

Explanation

Under the Transtheoretical Model (TTM / 阶段变化理论): (1) Precontemplation (无打算阶段): Client has no intention to change within the next 6 months and may be unaware or defensive. The optimal strategy is Consciousness Raising (提高认知) and emotional arousal (highlighting personal health risks and benefits of healthy eating) without imposing coercive action plans. (2) Contemplation (打算阶段): Weighing pros and cons. (3) Preparation (准备阶段): Setting SMART goals. (4) Action (行动阶段): Implementing changes. (5) Maintenance (维持阶段): Relapse prevention.

Question 46Nutrients, digestion and metabolic reasoning

In human nutritional energetics, what are the physiological energy coefficients (能量系数) for carbohydrates, lipids (fats), and proteins per gram under Chinese national nutrition standards?

  1. Carbohydrates: 4.0 kcal/g (16.7 kJ/g); Lipids: 9.0 kcal/g (37.6 kJ/g); Proteins: 4.0 kcal/g (16.7 kJ/g) Correct answer.
  2. Carbohydrates: 9.0 kcal/g (37.6 kJ/g); Lipids: 4.0 kcal/g (16.7 kJ/g); Proteins: 4.0 kcal/g (16.7 kJ/g)
  3. Carbohydrates: 4.0 kcal/g (16.7 kJ/g); Lipids: 7.0 kcal/g (29.3 kJ/g); Proteins: 4.0 kcal/g (16.7 kJ/g)
  4. Carbohydrates: 2.0 kcal/g (8.4 kJ/g); Lipids: 9.0 kcal/g (37.6 kJ/g); Proteins: 7.0 kcal/g (29.3 kJ/g)

Explanation

Under standard human nutritional energetics and Chinese DRIs, the physiological energy conversion coefficients (能量系数 / Atwater energy factors) are 4.0 kcal/g (16.7 kJ/g) for carbohydrates, 9.0 kcal/g (37.6 kJ/g) for dietary lipids/fats, and 4.0 kcal/g (16.7 kJ/g) for proteins. Ethanol yields approximately 7.0 kcal/g (29.3 kJ/g) but is not an essential nutrient.

Question 47Nutrients, digestion and metabolic reasoning

Which option lists all nine amino acids considered essential for adult humans?

  1. Lysine, Tryptophan, Phenylalanine, Methionine, Threonine, Isoleucine, Leucine, Valine, and Histidine Correct answer.
  2. Adults: Lysine, Tyrosine, Phenylalanine, Cysteine, Threonine, Isoleucine, Leucine, Valine; Infants: Arginine
  3. Adults: Alanine, Tryptophan, Phenylalanine, Methionine, Serine, Isoleucine, Leucine, Valine; Infants: Glycine
  4. Adults: Lysine, Glutamine, Phenylalanine, Methionine, Threonine, Asparagine, Leucine, Valine; Infants: Taurine

Explanation

The nine amino acids considered essential in adults are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The older eight-amino-acid adult list that treats histidine as essential only in infancy is outdated.

Question 48Nutrients, digestion and metabolic reasoning

When evaluating protein quality using the Amino Acid Score (AAS / 氨基酸评分), what is the first limiting amino acid (第一限制氨基酸) most commonly found in cereal grains such as rice and wheat flour?

  1. Methionine (蛋氨酸)
  2. Lysine (赖氨酸) Correct answer.
  3. Tryptophan (色氨酸)
  4. Valine (缬氨酸)

Explanation

In cereal proteins (rice, wheat, corn), Lysine (赖氨酸) is the most deficient essential amino acid relative to the reference human requirement pattern, making it the first limiting amino acid (第一限制氨基酸). In contrast, legumes (soybeans) are rich in lysine but limited in sulfur-containing amino acids (Methionine/Cysteine).

Question 49Nutrients, digestion and metabolic reasoning

In protein nutritional evaluation, how is Protein Biological Value (BV / 蛋白质生物价) calculated from nitrogen balance parameters?

  1. BV = (Retained Nitrogen / Absorbed Nitrogen) × 100 Correct answer.
  2. BV = (Absorbed Nitrogen / Ingested Nitrogen) × 100
  3. BV = (Retained Nitrogen / Ingested Nitrogen) × 100
  4. BV = (Fecal Nitrogen / Urinary Nitrogen) × 100

Explanation

Protein Biological Value (BV / 生物价) reflects the efficiency with which absorbed protein nitrogen is retained and utilized for maintenance and tissue synthesis. The formula is: BV = (Retained Nitrogen [储留氮] / Absorbed Nitrogen [吸收氮]) × 100, where Absorbed N = Ingested N - (Fecal N - Metabolic Fecal N) and Retained N = Absorbed N - (Urinary N - Endogenous Urinary N).

Question 50Nutrients, digestion and metabolic reasoning

Which of the following pairs of polyunsaturated fatty acids are classified as strictly essential fatty acids (必需脂肪酸) for humans because human desaturase enzymes cannot introduce double bonds beyond carbon 9?

  1. Linoleic acid (亚油酸, 18:2 n-6) and alpha-Linolenic acid (α-亚麻酸, 18:3 n-3) Correct answer.
  2. Oleic acid (油酸, 18:1 n-9) and Palmitic acid (软脂酸, 16:0)
  3. Arachidonic acid (花生四烯酸, 20:4 n-6) and Stearic acid (硬脂酸, 18:0)
  4. Eicosapentaenoic acid (EPA, 20:5 n-3) and Docosahexaenoic acid (DHA, 22:6 n-3)

Explanation

Humans lack delta-12 and delta-15 desaturase enzymes and therefore cannot synthesize Linoleic acid (LA, 18:2 n-6) or alpha-Linolenic acid (ALA, 18:3 n-3) de novo from oleic acid or acetyl-CoA. LA and ALA are the two strictly essential fatty acids (必需脂肪酸) from which longer-chain PUFAs (arachidonic acid, EPA, DHA) can be downstream-synthesized.