Question

---Has Sam finished his homework today?

---I have no idea．He ________ it this morning．

1. A.
   did
2. B.
   has done
3. C.
   was doing
4. D.
   had done

Answer 1

C
此题语境设计非常精彩，句意是：“Sam做完作业了吗?”“我不知道。他今天早晨正在做。”本题考查的是过去某个时间正在做的事情，所以选择C项。