--- Do we have to hand in our research reports this afternoon, Professor Smith?
--- Yes, you . I will be waiting to check them all the afternoon.
A. should
B. may
C. can
D. must
网友回答
A. should
B. may
C. can
(答案→)D. must
解析：——史密斯教授，我们必须今天下午上交我们的研究报告吗？
——是的，你们必须上交。下午我将要等待查看它们（研究报告）全部。
故应选D。A. should 应该 B. may 也许 C. can 能