Subject and Object Questions: Who Called? Who Did You Call? (A2 Grammar)

Is the person at the start of the answer (My brother called me)? Then put the past form right after Who, with no did.

Who called? (no did)

Who did you call? (did)

Is the person after the verb (I called my brother)? Then use did + the base verb: Who did you call?

What happened?

What happened? asks about an event. The past form comes right after What, with no did.

Where is the answer?

Look at the answer. Is the person at the start, before the verb? Ask with no did. Is the person after the verb? Ask with did.

What are the common mistakes?

IncorrectCorrectWhy
Who did call you?Who called you?My brother is at the start of the answer, so there is no did.
Who you called?Who did you call?The answer comes after the verb (I called my brother), so you need did.
What did happen?What happened?No did in What happened?