Justina used to be the best-behaved girl, … ?

Analyze the question

This is a question tag. The sentence is "Justina used to be the best-behaved girl, ____?" We need the correct tag to match the main clause.

Explain the concept

A question tag uses the auxiliary verb of the main clause, and the tag is negative after a positive statement. With "used to," there are two accepted forms:

• Formal or traditional: "used to" is treated as a main verb in the past tense, so the tag is didn't + subject ("She used to be late, didn't she?"). This is the form most Nigerian exam texts accept.
• Other form: "used not to" or "usedn't she" is rare and old-fashioned, and it is not offered here.

Step-by-step solution

1. The main clause is positive: "Justina used to be the best-behaved girl."
2. So the tag must be negative.
3. The subject is "Justina," which becomes the pronoun she.
4. The verb phrase is "used to," which is past tense and takes the auxiliary did → didn't.
5. Check the other options: • A. couldn't she uses the modal "could," which is not in the sentence. • B. wasn't she picks up the "be" after "to," but "be" is the infinitive, not the main auxiliary. This is a common trap. • C. wouldn't she uses "would," which is not in the sentence. • D. didn't she matches "used to" as a past-tense verb. ✔

Answer: D. didn't she

The correct sentence is: "Justina used to be the best-behaved girl, didn't she?

Tip: For tags, ignore what comes after "used to." Look only at "used," which is past tense, and use didn't. Don't be tricked by the "be" that follows.