问题
选择题
--- I saw the Smiths at West Beijing Station this afternoon.
--- You __________. They are still on holiday in Hawaii.
A．mustn't have
B．shouldn't
C．couldn't have
D．needn't
答案
答案：C
题目分析:考查情态动词。从语境判断此处的情态动词是表示对过去的推测，应该用情态动词+have done，而must表示推测只用于肯定句，所以C选项正确。句意：---我今天下午在北京西站看到史密斯夫妇了。---你不可能看见他们。他们现在还在夏威夷度假呢。