Question

— Has Sam finished his homework today ?

— I have no idea. He ______ it this morning.

A. did       B. has done        C. was doing      D. had done

Answer 1

C

解析:

根據后面時間狀語this morning可判斷為過去時，排除B；進行體表示“示完成性，暫時性，感情色彩”。結合上句，不知道Sam是否做完，所以C 項是最佳答案。