一、"疑问词+不定式"的构成：由疑问代词who,whom,what,which; 疑问副词when,how,where等+不定式构成.
Choosing what to eat is no longer as easy as it once was.选择吃什么,已经不像以前那么简单了.
How to describe people is today's topic.如何描述人物是今天的话题.
二 、"疑问词+不定式"的功能：在句中可作主语、宾语、表语等成分.
1.作主语
How to give advice in English is what I am trying to learn.我正在努力学习如何用英语提建议.
2.作宾语
①作动词的宾语
We have to start somewhere if we want to learn how to write plays.我们要学习写剧本,总得有个开头.
②作介词的宾语
We had better learn to make the right choices about what and how we eat.我们最好能学会正确选择吃什么、怎么吃.
When you are trying to advise someone about what to do or what not to do,you can use should / ought to or should not /ought not to.当你想要建议某人做什么或者不做什么时,你可以用should / ought to 或者 should not / ought not to.
3.作表语
My question is where to find the answer.我的问题是在哪里能找到答案.
三、"疑问词+不定式"的使用方法.
⒈ "疑问词+不定式"构成的短语在句中当"名词"用,可以写成相应的从句.
I am not sure how to behave at the dinner table.(= I am not sure how I should behave at the dinner table.) 对餐桌礼仪,我心中没底儿.
⒉ 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)
疑问代词须接及物动词或相当于及物动词的短语
【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.
⒊ 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.
疑问副词后要接不及物动词；若要接及物动词,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.)
多留心一些类似的句子,自然而然就容易记住了.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)疑问代词须接及物动词或相当于及物动词的短语【误】 I don't know what to talk. 【正】 I don't know what to talk about.没看懂。。。因为talk是不及物动词，所以必须要加上介词about。再比如 He buys a house to live in.因为live是不及物动词，in不能少是不及物动词，后面就必须要跟介词吗，那arrive呢？不是说必须接介词，而是不能直接带宾语，要想带宾语，必须加介词arrive 后要想加地点的话，必须加at 或in