how to do 是指方式，what to do 是指对象！ how to do常与with连用。 how to do it how to deal with
what to do what to do with
what to do补充成完整表达就是have what to do（有什么事情要做，what可以等效替换成sth），其中的what类似于汉语中的“兼语”（what作have的宾语，同时兼作do的宾语），严格地说此处的to do应该为to be done，但由于英语中“将错就错”和“以讹传讹”的缘故，大家图简单都习惯了用“主动”形式来表示“被动”。
how to do it补充成完整表达就是know how to do it（知道如何去做某事）。其中，do it是动宾结构，to do是不定式（用于连接2个连续的行为动词，并把后面的行为动词“非谓语化”，以保证一个句子只有一个谓语，how作to do的方式状语，how to do it一起作know的补语。
简言之，what to do强调动作的对象what，结构上what就是do的宾语，而how to do it强调动作的方式how，必须要有个it去作do的宾语，否则句子结构上不完整。
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。
有点值得特别注意的是：当这结构当宾语时，它的作用等于名词分句，例如：
● I could not decide which dictonary to buy. / I could not decide which dictionary I should buy.
● Jack did not know where to find such a good teacher./ Jack did not know where he could find such a good teacher.
有些动词，如“ask, show, tell, advise, inform, teach”等，可以先有个宾语，然后才接着加上适当的“疑问词+不定式动词” 结构。例如：
● The chief technician showed the apprentice how to repair the machine.
● Have you told him where to get the application form?
综上所述，可见“疑问词+不定式动词”结构是个形象清新，既容易用又不容易出错的特别结构，可以多多运用。
“疑问词+不定式”结构小结
2010-04-06 21:25
“疑问词+不定式”结构小结
疑问词+不定式”是英语中很有用的结构。疑问词是疑问代词“who, whom, what, which, whose”和疑问副词“when, where, how”。
一、几种用法：
⑴作主语。如：
● When to hold the meeting has not yet been decided.
⑵作宾语。如：
● We must know what to say at a meeting.
⑶作表语。如：
● The problem is where to find the financial aid.
⑷作同位语。如：
● Tom had no idea which book to read first.
⑸用于双重宾语。如：
● I can tell you where to get this book.
二、注意事项：
1、并非所有动词都适用于“疑问词+不定式”结构，主要有：“know, see, decide, tell, ask, consider, discover, explain, forget, learn, remember, wonder, understand”等。
2、当这个结构作宾语时，它的作用相当于名词性从句。如：
● I could not decide which dictionary to buy. / I could not decide which dictionary I should buy.
● Jack did not know where to find such a good teacher./ Jack did not know where he could find such a good teacher.
3、有些动词，如“ask, show, tell, advise, inform, teach”等，可以先有个宾语，然后再接适当的“疑问词+不定式” 结构。如：
● Have you told him where to get the application form?
4、这种结构中，疑问代词须接及物动词或相当于及物动词的短语(who, which除外)
【误】 I don't know what to talk.
【正】 I don't know what to talk about.
但可以说：We haven't decided who (which) to go. 我们还没定谁(哪个)去。
5这种结构中的疑问副词后要接不及物动词；若接及物动词, 要有动词的宾语。
I don't know how to talk. 我不知如何谈。
I wonder if you could tell me how to do it. 不知您能否告诉我如何去做这件事。(不能说: ... how to do.)
三、考点例析：
1. There isn't any difference between the two. I really don't know ________.
A. where to choose
B. which to choose
C. to choose what
D. to choose which
考点："疑问词＋不定式"的语序；疑问词的选用。
2. I've worked with children before, so I know what ________ in my new job.
A. expected B. to expect C. to be expecting D. expects
考点：疑问词后接动词的用法。
家好，“疑问词 + 动词不定式”构成的不定式短语是本话题的语法“主角”。想了解它的更多知识，请关注以下三个看点：
第一看点： “疑问词 + 动词不定式”的个性
此结构中疑问词包括疑问代词who, what, which以及疑问副词when, where, how等（不与why连用）。这些“疑问词 + 动词不定式”结构经常放在forget, find out, discuss, decide, tell, teach, know, learn, wonder, remember等动词之后作宾语。如：
I don't know what to do. 我不知道该做什么。
He told me how to answer all the questions in English. 他告诉我怎样用英语回答所有的问题。
第二看点：“疑问词 + 动词不定式”的功用
“疑问词 + 动词不定式”结构在句子中可以用作宾语、主语和表语等。如：
How to do it is a question. 如何做是个问题。（用作主语）
He knows what to do and what not to do. 他知道该做什么，不该做什么。（用作动词宾语）
The question is how to put it. 问题是应该把它如何放才好。（用作表语）
第三看点：“疑问词 + 动词不定式”的转换
“疑问词 + 动词不定式”结构相当于一个名词性从句，常常可用同等成分的从句代替。改写后的句子需要在疑问词后加上相对应的主语，并要注意主谓语单复数的一致性。如：
The question is where to put it. →The question is where we should put it. 问题是应该把它放在哪里才好。
一些动词如tell, know, ask, show, teach, find (out), forget等都可接“疑问代（副）词（why除外） + 不定式”作宾语，充当简单句，其意义相当于一个宾语从句。这种句式可转化为含宾语从句的复合句。当然在句型转换中，并非所有的宾语从句都能转换为“疑问词 + 不定式”结构。
看一下下面的情况：
主句的谓语动词是decide, hope, wish, know, forget等时，句子中的“疑问词 + 动词不定式”结构可转化为宾语从句。此时从句的主语和主句的主语相同。如：
We can't decide when to start. →We can't decide when we should start.
We don't know what to do next. →We don't know what we should do next.
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