--Is Professer Smith giving the speech today?
--It be him. He is abroad right now.
A. mustn't
B. needn't
C. won't
D. can't
网友回答
A. mustn't
B. needn't
C. won't
(答案→)D. can't
解析：句意：--史密斯教授今天做演讲吗?--那是不可能的，他现在在国外。mustn't禁止； needn't不必；won't将不；can't 不可能。这里根据He is abroad right now.所以确定不可能是他，故选D。