Do not patch the underline in isolation. Read the whole sentence, and often the one before it. A choice can look fine until the period. Passage order is in English passage strategy.
The underline is not the unit
Verb tense, pronouns, and commas all depend on words outside the underline. Tense as a set is in verb tense. Least acceptable items still need the full sentence, in least acceptable questions.
Grammar overall is in ACT grammar rules.
The bottom line
Read past the underline. The trap is a local fix that breaks the sentence.
Start practicing
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