Least acceptable means three choices all work and one does not. You are hunting the broken one. Read the stem twice. Question types as a set are in English question types.
Flip the usual habit
Most English items want the best repair. This one wants the choice that introduces a grammar error, a wrong word, or a broken idiom. Read the whole sentence, not just the underline, in read the full sentence.
Illustration items are a different rhetorical job, in best-illustration questions. Grammar overall is in ACT grammar rules.
The bottom line
Three acceptable, one not. Pick the one that breaks the sentence.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
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