If she had known, she wouldn't have come, … ?

Analyze the question: This is a question tag. The main clause is "she wouldn't have come". The "If she had known" part is just a subordinate clause, so the tag depends on the main clause.

Concept: The rule for question tags is:

• A positive statement takes a negative tag.
• A negative statement takes a positive tag.
• The tag repeats the auxiliary verb of the main clause and uses the matching pronoun.

Solution:

1. Main clause: "she wouldn't have come". It is negative.
2. The auxiliary verb is would (wouldn't = would not).
3. Because the statement is negative, the tag must be positive: would she?
4. The pronoun is "she", which matches the subject.

The full sentence is: If she had known, she wouldn't have come, would she?

Why the other options are wrong:

• A. "could she" uses the wrong auxiliary. The sentence has "would", not "could".
• B. "couldn't she" has the wrong auxiliary and is also negative, so it does not reverse the polarity.
• C. "wouldn't she" is negative after a negative statement. A tag must have the opposite polarity.

Answer: D. would she

Exam tip: Ignore the "if" clause and look only at the main clause. Then flip the polarity: negative becomes positive, and positive becomes negative. Keep the same auxiliary verb.