- I saw the Smiths at West Beijing Station this afternoon.You . They are still on h

问题补充：

--- I saw the Smiths at West Beijing Station this afternoon.

--- You . They are still on holiday in Hawaii.

A. mustn have

B. shouldn

C. couldn have

D. needn

答案：

A. mustn have

B. shouldn

(答案→)C. couldn have

D. needn

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。