Writing: Sentence Boundaries, Agreement, and Clarity
The core skills
Writing items test standard edited English: complete sentence boundaries, subject-verb agreement, pronoun agreement and case, consistent verb tense, correct modifiers, parallel structure, punctuation (comma, semicolon, colon, apostrophe), transitions, and conciseness. Many questions are rhetorical - you choose the revision that best supports a stated goal for the paragraph, so read the prompt line above the choices.
Traps
- Comma splices. Two independent clauses need a period, semicolon, or comma plus a coordinating conjunction (and, but, so, yet, for, or, nor). However and therefore are not conjunctions; joining clauses with them plus a comma is an error.
- Interrupting phrases. In The box of old letters was in the attic, the verb agrees with box, not letters. Cross out prepositional phrases to check.
- Dangling modifiers. An opening phrase must describe the subject that follows it.
- Apostrophes. Its is possessive; it's means it is. Plural nouns take s, possessives take 's.
- Over-correction. The longest, most formal option is often wrong. If two choices are grammatically fine, pick the shorter one that keeps the meaning.
Rule of thumb
Strip a sentence to subject plus verb. If those two do not agree, or if the stripped version is not a complete thought, you have found the error.
Worked example
Walking to the store, the rain began. The opening phrase describes the walker, but the subject is rain - a dangling modifier. Fix it: Walking to the store, I was caught in the rain.