问题补充:
—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
答案:
A. did
B. has done
(答案→)C. was doing
D. had done
解析:考查时态题。题意为“他今天上午在做作业,但是我不知道他现在是否做完了”,用过去进行时强调过去某时正在做某事,另外,过去进行时,还表示动作的未完成性。故最佳答案为C。