ACT English: Usage, Punctuation, and Rhetorical Skill
The ACT English test measures two intertwined skill sets: standard English conventions and rhetorical effectiveness. On the conventions side, know subject-verb agreement (especially when a prepositional phrase separates subject from verb), pronoun case and agreement, verb tense consistency, and modifier placement. Punctuation is heavily tested: commas with nonessential clauses, semicolons joining independent clauses, colons introducing lists or explanations, and dashes marking parenthetical material. Learn the difference between a comma splice and a correct semicolon or period.
On the rhetorical side, expect questions about relevance, transitions, paragraph organization, concision, and tone. A common trap is the "add a sentence" question: test whether the sentence supports the paragraph's main idea. Another trap is redundancy-answer choices that repeat an idea already stated. Prefer the most concise option that preserves meaning, but never sacrifice clarity for brevity.
Worked example
Sentence: "The museum, which opened in 1998, houses a large collection." The phrase "which opened in 1998" is nonessential, so commas are correct. If removing the phrase changes the meaning (essential clause), use no commas. Rule of thumb: if the clause can be lifted out without confusing the reader, set it off with commas.
Read each sentence in context. Many wrong answers are grammatically fine but rhetorically wrong for the passage.