—Has Billy finished his homework today?
—I have no idea.He it this morning.
A. would do
B. was doing
C. has done
D. had done
网友回答
A. would do
(答案→)B. was doing
C. has done
D. had done
解析：依据答语中的时间状语可推知，比利作业未完成。他今天上午一直在做。过去进行
时除表示某段时间内一直在进行的动作外，还可表示某时刻正在进行的动作。如：
I was reading a book when he came in.