Student or Learner
Which tense is the most appropriate in the following context? If they are all possible, can you explain the difference in nuance?
A: I have broken your favourite vase. I'm so sorry.
B: Oh, no! What [did you do/have you done/were you doing]?
"What have you done?" has just been answered. You normally ask a question before the answer is given.
"What did you do?" shares a similar problem to the above. He broke your vase. You know that.
More common would be a "How" question. "How did you manage to do that?!" "What were you doing" has the merits of including an implicit 'how'. "What were you doing that led to your breaking my vase?"