---- 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
网友回答
A. did
B. has done
(答案→)C. was doing
D. had done
解析：考查时态。句意：今天Sam完成作业了吗？我不知道，他今天上午在做。表示过去某一时刻进行的动作用过去进行时态。根据题意上午那个时刻他在做作业，故选C。