英语有个很有用的结构，就是：疑问词+不定式动词（question word + to-infinitive）。

　　疑问词是疑问代词who, whom, what, which, whose和疑问副词when, where, how, why 。此外，连接词whether也适用。

　　疑问词+不定式动词结构有何功用呢？其主要功用有下列五种：

　　⑴当主语，如：

　　● When to hold the meeting has not yet been decided.

　　● Where to live is a problem.

　　● How to cope with the rising cost of living becomes a daily discussion topic.

　　⑵当宾语，如：

　　● We must know what to say at a meeting.

　　● He could not tell whom to trust.

　　● Do you know how to play bridge?

　　⑶当补足语，如：

　　● The problem is where to find the financial aid.

　　● The question is who to elect.

　　⑷当名词同位语，如：

　　● Tom had no idea which book to read first.

　　● Do you have a rough impression how to do it?

　　⑸当宾语补足语，如：

　　● Jim is not sure whose to choose.

　　● Mary and John are not certain whether to get married or not.

　　适用于疑问词+不定式动词的动词包括：know, see, decide, tell, ask, consider, discover, explain, forget, guess, hear, imagine, inquire, learn, remember, think, wonder, understand等。

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