Correct Answer:
C. When did your friends come?
Correct answer: When did your friends come?. In a past-tense question with “did”, the main verb stays in its base form: “When did your friends come?”
Background: The helping verb “did” already carries the past tense.
- When have your friends come?: “Have … come” does not fit a question about a specific past time.
- When did your friends came?: “Did … came” wrongly puts the verb in the past tense after “did”.
- When your friends have come?: This is not in correct question form.
Did you know? The same rule applies to “Did he go?” (not “Did he went?”).
Memory trick: Did + base verb.