If you watch carefully you can see the man does the trick.A. whoB. whatC. howD. which

问题补充：

If you watch carefully, you can see the man does the trick.

A. who

B. what

C. how

D. which

答案：

A. who

B. what

(答案→)C. how

D. which

解析：考查宾语从句的引导词。句意“如果仔细观察，你能看到那个人是怎样表演杂技的。”宾语从句不缺少句子成分，故用副词引导，how“如何，怎样”，符合题意。故选C。