--- 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
网友回答
A. mustn't have
B. shouldn't
(答案→)C. couldn't have
D. needn't
解析：
试题分析: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。