---Who cleaned the classroom?---Mary .A. canB. doesC. didD. is

问题补充：

---Who cleaned the classroom?

---Mary .

A. can

B. does

C. did

D. is

答案：

A. can

B. does

(答案→)C. did

D. is

解析：此题考查过去时的简略回答，因其谓语动词是行为动词故其简略回答要用did。