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Odisha BSE Madhyama Science study materials
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Odisha BSE Madhyama Science practice questions

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Question 1Science

Which gas is released when dilute hydrochloric acid reacts with zinc granules during a school laboratory activity?

  1. Chlorine
  2. Carbon dioxide
  3. Hydrogen Correct answer.
  4. Oxygen

Explanation

Zinc is a metal above hydrogen in the reactivity series, so it displaces hydrogen from the dilute acid. The gas bubbles produced are hydrogen, which burns with a pop sound when a burning splint is brought near the test tube. Carbon dioxide would need a carbonate, not a metal.

Question 2Science

A student observes that a beam of sunlight passing through a dusty room becomes visible, while the same beam is invisible in a clean room. Which property of the dust particles explains this?

  1. They absorb all wavelengths of light completely
  2. They scatter light of suitable wavelengths Correct answer.
  3. They reflect light only in a single direction
  4. They refract light into separate colours

Explanation

Fine suspended particles scatter light whose wavelength is comparable to or smaller than the particle size, so the beam becomes visible from the side. This is the Tyndall effect, which also explains why sunlight is scattered by mist and smoke. Absorption alone would make the beam dark, not visible.

Question 3Science

In a food chain, only about ten percent of the energy at one trophic level is transferred to the next. What is the main reason for this large loss?

  1. Energy is destroyed completely at each level
  2. Energy is stored permanently in the bodies of consumers
  3. Energy is converted into new matter at each level
  4. Most energy is lost as heat during respiration and in waste Correct answer.

Explanation

Organisms use most of the energy they obtain for respiration, movement, and maintenance, and much of it leaves as heat. Undigested material is egested as waste, so only a small fraction becomes new body mass available to the next level. Energy is never destroyed; it is transformed and dispersed.

Question 4Science

Which of the following is the correct chemical formula of washing soda?

  1. NaHCO3
  2. NaOH
  3. Na2CO3·10H2O Correct answer.
  4. NaCl

Explanation

Washing soda is hydrated sodium carbonate, written as Na2CO3·10H2O, and it is used in the laboratory and in laundry. On heating, it loses its water of crystallisation to form anhydrous sodium carbonate. Sodium bicarbonate is baking soda, and sodium hydroxide is caustic soda.

Question 5Science

A person suffering from a deficiency of vitamin C is most likely to show which symptom?

  1. Night blindness and dry eyes
  2. Weak bones with bent legs in children
  3. Swelling of the neck due to an enlarged thyroid
  4. Bleeding gums and slow wound healing Correct answer.

Explanation

Vitamin C is needed for the synthesis of collagen, the protein that strengthens skin, gums, and blood vessels. Its deficiency causes scurvy, marked by bleeding gums, loose teeth, and poor wound healing. Citrus fruits and amla are good sources.

Question 6Science

An object is placed between the pole and the principal focus of a concave mirror. Which statement correctly describes the image formed?

  1. Real, inverted, and of the same size
  2. Virtual, inverted, and smaller than the object
  3. Virtual, erect, and larger than the object Correct answer.
  4. Real, inverted, and smaller than the object

Explanation

When the object lies between the pole and the focus of a concave mirror, the reflected rays diverge and the image forms behind the mirror. Such an image is virtual, erect, and magnified, which is why concave mirrors are used as shaving mirrors. Real images from a concave mirror require the object to be beyond the focus.

Question 7Science

Which part of the human respiratory system contains the tiny balloon-like sacs where exchange of gases takes place?

  1. Bronchi
  2. Alveoli Correct answer.
  3. Trachea
  4. Larynx

Explanation

Alveoli are thin-walled sacs at the ends of the bronchioles, surrounded by a network of blood capillaries. Their large total surface area and thin walls allow oxygen to diffuse into the blood and carbon dioxide to diffuse out. The trachea and bronchi are only conducting tubes.

Question 8Science

A current of 2 A flows through a resistor of 15 ohm for 5 minutes. How much heat energy is produced in the resistor?

  1. 3000 J
  2. 150 J
  3. 9000 J
  4. 18000 J Correct answer.

Explanation

Joule's law gives heat as I squared times R times t. Here I = 2 A, R = 15 ohm, and t = 5 minutes = 300 s, so heat = 4 x 15 x 300 = 18000 J. Care must be taken to convert minutes into seconds before substituting.

Question 9Science

Which of the following is a characteristic property of ionic compounds such as sodium chloride?

  1. They are soft and have low melting points
  2. They conduct electricity in the molten state Correct answer.
  3. They exist as individual molecules in the solid state
  4. They dissolve readily in petrol and kerosene

Explanation

Ionic solids consist of oppositely charged ions held in a rigid lattice. When melted or dissolved in water, these ions become free to move and carry current, so the molten compound conducts electricity. In the solid state the ions are fixed and cannot conduct.

Question 10Science

Which group of organisms in a pond ecosystem acts as decomposers?

  1. Small fish and tadpoles
  2. Water snails and insects
  3. Bacteria and fungi Correct answer.
  4. Green algae and duckweed

Explanation

Decomposers break down dead plants and animals and release nutrients back into the soil or water. Bacteria and fungi perform this role in most ecosystems, including ponds. Algae are producers, while fish and snails are consumers.

Question 11Science

A solution turns red litmus blue, gives a white precipitate with dilute hydrochloric acid that dissolves on adding excess of the acid, and is used to test carbon dioxide. Which compound is most likely present?

  1. Copper sulphate
  2. Calcium hydroxide Correct answer.
  3. Ammonium chloride
  4. Sodium chloride

Explanation

Calcium hydroxide solution is lime water, which is basic and turns red litmus blue. It gives a milky white precipitate of calcium carbonate when carbon dioxide is passed through it, and the precipitate dissolves in excess acid. These properties together identify it.

Question 12Science

Which of the following is the correct order of the parts of the human digestive tract through which food passes?

  1. Mouth, oesophagus, small intestine, stomach, large intestine
  2. Mouth, stomach, small intestine, oesophagus, large intestine
  3. Mouth, stomach, oesophagus, large intestine, small intestine
  4. Mouth, oesophagus, stomach, small intestine, large intestine Correct answer.

Explanation

Food travels from the mouth through the oesophagus into the stomach, then into the small intestine, where most digestion and absorption occur. The remaining material passes into the large intestine before being egested. The order reflects the continuous alimentary canal.

Question 13Science

Two resistors of 6 ohm and 3 ohm are connected in parallel across a 6 V battery. What is the total current drawn from the battery?

  1. 3 A Correct answer.
  2. 0.67 A
  3. 9 A
  4. 2 A

Explanation

For parallel resistors the equivalent resistance is given by 1/R = 1/6 + 1/3 = 1/2, so R = 2 ohm. The total current is V/R = 6/2 = 3 A. The same current could also be found by adding the branch currents 1 A and 2 A.

Question 14Science

Which of the following statements about the process of photosynthesis is correct?

  1. It takes place only during the night
  2. It converts light energy into chemical energy in glucose Correct answer.
  3. It occurs only in the roots of green plants
  4. It releases carbon dioxide and uses oxygen

Explanation

In photosynthesis, chlorophyll traps light energy and uses it to combine carbon dioxide and water into glucose, storing energy in chemical bonds. Oxygen is released as a by-product. The process requires light and occurs mainly in the leaves.

Question 15Science

A convex lens of focal length 10 cm forms a real image of an object placed 30 cm from the lens. Using the lens formula, what is the image distance?

  1. 15 cm Correct answer.
  2. 5 cm
  3. 30 cm
  4. 20 cm

Explanation

The lens formula is 1/f = 1/v minus 1/u. Taking u = -30 cm and f = +10 cm gives 1/v = 1/10 - 1/30 = 2/30, so v = 15 cm. The positive sign shows a real image on the other side of the lens.

Question 16Science

Which of the following pairs correctly matches a disease with its causative organism type?

  1. Malaria - virus
  2. Ringworm - bacterium
  3. Tuberculosis - bacterium Correct answer.
  4. Dengue - protozoan

Explanation

Tuberculosis is caused by Mycobacterium tuberculosis, a bacterium, and it mainly affects the lungs. Malaria is caused by a protozoan, dengue by a virus, and ringworm by a fungus. Matching each disease to its pathogen group is essential for prevention and treatment.

Question 17Science

A student adds iron filings to copper sulphate solution and observes a colour change. Which conclusion is supported by this observation?

  1. Copper is more reactive than iron
  2. Iron is more reactive than copper Correct answer.
  3. No chemical reaction has taken place
  4. Both metals have equal reactivity

Explanation

Iron displaces copper from copper sulphate because iron is more reactive and lies above copper in the reactivity series. The blue colour fades as green iron sulphate forms and reddish-brown copper is deposited. A displacement reaction always proceeds when the added metal is higher in the series.

Question 18Science

Which of the following is a renewable source of energy that is directly derived from the Sun's radiation reaching the Earth's surface?

  1. Coal
  2. Solar energy Correct answer.
  3. Natural gas
  4. Petroleum

Explanation

Solar energy is obtained directly from sunlight and is continuously replenished, so it is renewable. Coal, petroleum, and natural gas are fossil fuels formed over millions of years and are exhaustively used. Their reserves cannot be replaced within a human lifetime.

Question 19Science

A sound wave travels from air into water. Which quantity remains unchanged during this change of medium?

  1. Amplitude of the wave
  2. Speed of the wave
  3. Frequency of the wave Correct answer.
  4. Wavelength of the wave

Explanation

Frequency is determined by the source and does not change when a wave enters a new medium. The speed of sound is greater in water than in air, so the wavelength must increase to keep the product of frequency and wavelength equal to the speed. Amplitude changes with transmission losses at the boundary.

Question 20Science

Which of the following correctly describes the function of the ozone layer in the upper atmosphere?

  1. It supplies oxygen for the respiration of living organisms
  2. It traps heat and raises the Earth's average temperature
  3. It reflects radio waves back to the Earth's surface
  4. It absorbs most of the harmful ultraviolet radiation from the Sun Correct answer.

Explanation

Ozone in the stratosphere absorbs a large part of the Sun's ultraviolet radiation, protecting living organisms from harmful effects such as skin damage and mutations. Depletion of this layer by chlorofluorocarbons allows more ultraviolet light to reach the Earth. Oxygen for respiration comes from the lower atmosphere and photosynthesis.

Question 21Science

A car starts from rest and accelerates uniformly to a speed of 20 m/s in 8 s. What distance does it travel during this time?

  1. 320 m
  2. 40 m
  3. 160 m
  4. 80 m Correct answer.

Explanation

For uniform acceleration from rest, the distance is given by s = ut + half at squared with u = 0. The acceleration is 20/8 = 2.5 m/s squared, so s = half x 2.5 x 64 = 80 m. The same result follows from average velocity 10 m/s multiplied by 8 s.

Question 22Science

Which of the following is the correct sequence of events during the sexual reproduction of a flowering plant after pollination?

  1. Formation of fruit, fertilisation, germination of pollen tube, seed formation
  2. Fertilisation, germination of pollen tube, formation of fruit, seed formation
  3. Germination of pollen tube, fertilisation, formation of fruit, seed formation Correct answer.
  4. Germination of pollen tube, formation of fruit, fertilisation, seed formation

Explanation

After pollination, the pollen grain germinates on the stigma and its tube grows down the style towards the ovule. Fertilisation then occurs when a male gamete fuses with the egg, after which the ovule becomes the seed and the ovary develops into the fruit. The sequence follows the actual order of these developmental events.

Question 23Science

An electric bulb is marked 100 W, 220 V. What is the resistance of its filament when it operates at the rated voltage?

  1. 48.4 ohm
  2. 484 ohm Correct answer.
  3. 2.2 ohm
  4. 22 ohm

Explanation

Power is given by P = V squared / R, so R = V squared / P. Substituting V = 220 V and P = 100 W gives R = 48400/100 = 484 ohm. The current at this voltage would be about 0.45 A.

Question 24Science

A compound contains 40 percent carbon, 6.7 percent hydrogen, and 53.3 percent oxygen by mass, and its molecular mass is 60. What is its molecular formula?

  1. CH2O
  2. C3H6O3
  3. C2H4O2 Correct answer.
  4. C2H6O

Explanation

Dividing each percentage by the atomic mass gives the mole ratio C:H:O = 40/12 : 6.7/1 : 53.3/16 = 3.33 : 6.7 : 3.33, which simplifies to 1:2:1. The empirical formula is CH2O with mass 30, and since the molecular mass is 60 the molecular formula is twice this, C2H4O2. This corresponds to acetic acid.

Question 25Science

Which statement best explains why a person with a damaged cerebellum has difficulty in walking and balancing?

  1. The cerebellum regulates the rate of breathing and heartbeat
  2. The cerebellum carries impulses between the eye and the brain
  3. The cerebellum controls voluntary muscle coordination and balance Correct answer.
  4. The cerebellum is the centre for intelligence and memory

Explanation

The cerebellum, located at the back of the brain, coordinates voluntary movements and maintains posture and balance. Damage to it therefore causes unsteady gait and poor coordination. Breathing and heartbeat are controlled by the medulla, and memory is associated with the cerebrum.

Question 26Science

Which of the following is the SI unit of electric charge?

  1. Ampere
  2. Ohm
  3. Coulomb Correct answer.
  4. Volt

Explanation

Electric charge is measured in coulombs, defined as the charge that flows when a current of one ampere passes for one second. The ampere measures current, the volt measures potential difference and the ohm measures resistance, so only the coulomb is the unit of charge.

Question 27Science

Which of the following is the chemical name of common baking soda used in kitchens?

  1. Sodium chloride
  2. Sodium hydrogen carbonate Correct answer.
  3. Sodium carbonate
  4. Calcium carbonate

Explanation

Baking soda is sodium hydrogen carbonate, NaHCO3, which releases carbon dioxide on heating or on reaction with acid. Sodium carbonate is washing soda and calcium carbonate is limestone or chalk, so neither matches the kitchen substance.

Question 28Science

Which of the following is the largest gland in the human body, and secretes bile?

  1. Pancreas
  2. Thyroid gland
  3. Salivary gland
  4. Liver Correct answer.

Explanation

The liver is the largest gland in the human body and produces bile, which is stored in the gall bladder and helps in the digestion of fats. The pancreas and salivary glands are also glands but are far smaller and secrete different digestive juices.

Question 29Science

Which of the following is the correct chemical formula of quicklime, obtained by heating limestone strongly?

  1. CaSO4
  2. CaCO3
  3. Ca(OH)2
  4. CaO Correct answer.

Explanation

Strong heating of limestone, calcium carbonate, drives off carbon dioxide and leaves calcium oxide, called quicklime. Calcium hydroxide is slaked lime and calcium sulphate is gypsum, so only CaO fits the product of this heating.

Question 30Science

Which of the following is the unit in which the loudness of sound is commonly expressed?

  1. Decibel Correct answer.
  2. Metre
  3. Newton
  4. Hertz

Explanation

Loudness is related to the amplitude of a sound wave and is expressed in decibels. The hertz measures frequency, the metre measures wavelength and the newton measures force, so only the decibel describes loudness.

Question 31Science

Which of the following organisms is a unicellular organism that reproduces by binary fission?

  1. Amoeba Correct answer.
  2. Yeast
  3. Spirogyra
  4. Hydra

Explanation

Amoeba is a single-celled organism that reproduces asexually by simple binary fission, dividing into two daughter cells. Yeast reproduces mainly by budding, Spirogyra by fragmentation and Hydra by budding, so none of them fits binary fission.

Question 32Science

Which of the following is the value of acceleration due to gravity near the Earth's surface, commonly used in numerical problems?

  1. 3.7 m/s2
  2. 98 m/s2
  3. 9.8 m/s2 Correct answer.
  4. 1.6 m/s2

Explanation

Near the Earth's surface the acceleration due to gravity is about 9.8 metres per second squared, often rounded to 10 in rough calculations. Values near 1.6 and 3.7 belong to the Moon and Mars respectively, and 98 is ten times too large.

Question 33Science

Which of the following is a non-renewable source of energy among the choices given?

  1. Sunlight
  2. Tidal energy
  3. Wind
  4. Coal Correct answer.

Explanation

Coal is a fossil fuel formed over millions of years and its reserves are limited, so it is non-renewable. Wind, sunlight and tides are continuously replenished by natural processes and are therefore renewable sources.

Question 34Science

A body moves along a straight line with uniform velocity. Which statement about its acceleration is correct?

  1. Its acceleration increases steadily with time.
  2. Its acceleration is negative because the motion is uniform.
  3. Its acceleration equals its velocity.
  4. Its acceleration is zero because velocity does not change. Correct answer.

Explanation

Acceleration is the rate of change of velocity, so when velocity stays constant in both magnitude and direction the change is zero and acceleration is zero. A body moving uniformly does not speed up, slow down or turn, hence no acceleration acts on it.

Question 35Science

An object is placed 20 cm in front of a plane mirror. How far is the image from the object?

  1. 60 cm
  2. 20 cm
  3. 40 cm Correct answer.
  4. 10 cm

Explanation

A plane mirror forms an image as far behind the mirror as the object is in front of it, so the image lies 20 cm behind the mirror. The distance between object and image is therefore 20 cm plus 20 cm, which equals 40 cm.

Question 36Science

A solution of pH 3 is diluted ten times with pure water. Which statement about the resulting solution is correct?

  1. Its pH remains exactly 3.
  2. It becomes more acidic than before.
  3. It becomes less acidic, with pH higher than 3 but still below 7. Correct answer.
  4. It becomes neutral with pH 7.

Explanation

Dilution lowers the concentration of hydrogen ions, so the solution becomes less acidic and its pH rises. The diluted solution is still acidic, so its pH stays below 7 even though it is greater than the original value of 3.

Question 37Science

A plant is kept in darkness for two days and then a variegated leaf is tested with iodine solution. Only the green parts turn blue-black. Which conclusion follows?

  1. Starch is formed only in parts of the leaf that contain chlorophyll. Correct answer.
  2. The leaf absorbed iodine only through its veins.
  3. Respiration occurs only in the green parts of the leaf.
  4. Darkness is necessary for starch formation.

Explanation

The iodine test detects starch, and only the green regions turn blue-black, showing that starch was made there. Since green regions contain chlorophyll, the result supports the conclusion that chlorophyll is needed for photosynthesis and starch formation.

Question 38Science

Why does a clinical thermometer have a narrow constriction just above the bulb?

  1. To prevent mercury from returning to the bulb until it is shaken. Correct answer.
  2. To reduce the amount of mercury needed for accurate reading.
  3. To increase the sensitivity of the mercury to small temperature changes.
  4. To make the thermometer float in the liquid being measured.

Explanation

The kink or constriction stops mercury from flowing back into the bulb when the thermometer is removed from the patient's body. This allows the reading to be taken after removal, and the mercury returns only when the thermometer is shaken.

Question 39Science

Which of the following correctly explains why sodium chloride conducts electricity when molten but not when solid?

  1. In the solid state the ions are held in fixed positions, but melting frees them to move. Correct answer.
  2. Melting produces free electrons that carry the current.
  3. In the solid state the ions are free to move, but melting fixes them.
  4. Sodium chloride is a metal and conducts only when heated.

Explanation

Conduction in ionic solids requires mobile charged particles. In solid sodium chloride the ions are locked in a lattice and cannot move, but on melting the lattice breaks down and the ions become free to migrate towards the electrodes.

Question 40Science

A person's blood group is A. Which of the following statements about transfusion is correct?

  1. The person can receive blood only from group A and group O donors. Correct answer.
  2. The person has anti-A antibodies in the plasma.
  3. The person can donate blood safely to any group.
  4. The person can receive blood from any group without risk.

Explanation

A person of blood group A carries A antigens on red cells and anti-B antibodies in plasma, so group B blood would be attacked. Group A and group O red cells lack B antigen and are therefore compatible for transfusion.

Question 41Science

An electric iron of resistance 44 ohm is connected to a 220 V supply. What current flows through it?

  1. 5 A Correct answer.
  2. 0.2 A
  3. 10 A
  4. 20 A

Explanation

Ohm's law gives current as voltage divided by resistance, so 220 volts divided by 44 ohm equals 5 amperes. The power consumed would then be 220 times 5, that is 1100 watts, which is typical for an electric iron.

Question 42Science

Which of the following best explains why the sky appears blue to an observer on the Earth's surface?

  1. Blue light is emitted by the atmosphere itself.
  2. The atmosphere absorbs all colours except blue.
  3. Fine particles scatter shorter blue wavelengths more strongly than longer red wavelengths. Correct answer.
  4. Blue light travels faster than red light in air.

Explanation

Molecules and fine particles in the atmosphere scatter light of shorter wavelength much more strongly than longer wavelengths, a phenomenon called Rayleigh scattering. Blue light is therefore scattered towards the observer from all directions of the sky, giving it a blue appearance.

Question 43Science

Which of the following is the correct order of the stages of nutrition in an animal, from intake to removal of undigested matter?

  1. Digestion, ingestion, absorption, egestion, assimilation
  2. Absorption, ingestion, digestion, assimilation, egestion
  3. Ingestion, digestion, absorption, assimilation, egestion Correct answer.
  4. Ingestion, absorption, digestion, assimilation, egestion

Explanation

Nutrition begins with ingestion of food, followed by digestion into simpler substances. These are absorbed into the body, assimilated into cells, and the undigested residue is finally removed by egestion.

Question 44Science

A compound has the empirical formula CH2 and a molecular mass of 42. What is its molecular formula?

  1. C3H6 Correct answer.
  2. C2H4
  3. C4H8
  4. CH2

Explanation

The empirical formula mass of CH2 is 12 plus 2, that is 14. Dividing the molecular mass 42 by 14 gives 3, so the molecular formula is three times CH2, namely C3H6.

Question 45Science

Two bodies of masses 2 kg and 3 kg are placed 1 m apart. If the gravitational force between them is F, what happens to the force when the separation is doubled?

  1. It becomes half of F.
  2. It becomes four times F.
  3. It becomes one-fourth of F. Correct answer.
  4. It remains equal to F.

Explanation

Newton's law of gravitation states that the force is inversely proportional to the square of the distance between the bodies. Doubling the separation therefore reduces the force to one divided by two squared, that is one-fourth of its original value.

Question 46Science

A student observes that a convex mirror always forms a virtual, erect and diminished image of a real object. Which use follows most directly from this property?

  1. As a rear-view mirror in vehicles Correct answer.
  2. As a solar concentrator to focus sunlight
  3. As a projector lens to throw images on a screen
  4. As a shaving mirror to magnify the face

Explanation

A convex mirror gives a wide field of view with small, erect images, which suits a rear-view mirror in vehicles. A shaving mirror and a solar concentrator both need the converging action of a concave mirror.

Question 47Science

A 60 W bulb and a 100 W bulb, both marked for the same voltage, are connected in series across that voltage. Which bulb glows more brightly?

  1. The 60 W bulb, because its resistance is higher and it dissipates more power in series. Correct answer.
  2. Both glow with equal brightness.
  3. Neither glows because the series circuit is broken.
  4. The 100 W bulb, because it is rated at a higher power.

Explanation

The 60 W bulb has the higher resistance since power at a fixed voltage is inversely related to resistance. In a series circuit the same current passes through both, and power dissipated equals current squared times resistance, so the higher-resistance bulb glows more brightly.

Question 48Science

An object is placed exactly at the centre of curvature of a concave mirror. Which description of the image formed is correct?

  1. No image is formed at this position
  2. Real, inverted and highly magnified, formed at the focus
  3. Virtual, erect and magnified, formed behind the mirror
  4. Real, inverted and of the same size, formed at the centre of curvature Correct answer.

Explanation

When an object lies at the centre of curvature of a concave mirror, the reflected rays converge at the same point on the principal axis. The image is therefore real, inverted and of the same size as the object.

Question 49Science

In a Mendelian cross between a pure tall pea plant and a pure dwarf pea plant, the F1 plants are all tall. When these F1 plants are self-pollinated, what fraction of the F2 plants is expected to be dwarf?

  1. None
  2. Three quarters
  3. One quarter Correct answer.
  4. One half

Explanation

Tallness is dominant, so the F1 plants are heterozygous and carry one tall and one dwarf allele. Self-pollination gives F2 offspring in the ratio three tall to one dwarf, so one quarter are dwarf.

Question 50Science

A saturated hydrocarbon and an unsaturated hydrocarbon are each treated with bromine water. Which observation and explanation is correct?

  1. Both decolourise bromine water because both contain carbon-hydrogen bonds.
  2. The saturated hydrocarbon decolourises bromine water by addition, while the unsaturated one does not.
  3. Neither reacts with bromine water because both are hydrocarbons.
  4. The unsaturated hydrocarbon decolourises bromine water by addition, while the saturated one does not. Correct answer.

Explanation

Unsaturated hydrocarbons contain double or triple bonds that add bromine across them, so the reddish-brown colour of bromine water disappears. Saturated hydrocarbons have only single bonds and do not undergo this addition, so the colour persists.