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(Wh) questions with (who) or (what) can be about a subject or an object.
How can you tell if a question is about a subject or an object?
When the question is about a SUBJECT you use the: question word, verb, and the rest of the sentence. Never use DID when the question is about a subject.
When the question is about an OBJECT, you use the: Question word, AUXILIARY (DO present, DID, DOES present), SUBJECT, verb, and the rest of the sentence.