如何讲解"wh-+to do"结构

如何讲解"wh-+to do"结构

“特殊疑问词＋动词不定式”的用法归纳
一、疑问代词who, what, which等和疑问副词when, where, how等后面跟不定式,构成不定式短语.这种结构在句中可作主语、宾语、表语、宾语补足语等句子成分.如：
Where to go is still a question. 到哪里去还是个问题.（作主语）
I know where to find the boy. 我知道到哪里能找到这个男孩.（作动词know的宾语）
I asked her how to learn English. 我问她如何学英语.（作双重宾语）
We must first solve the problem of whom to serve. 我们必须首先解决为谁服务的问题.（作介词of的宾语）
The question is how to learn English well. 问题是怎样学好英语.（作表语）
1. 作主语：作主语时,谓语动词常用单数形式.例如：
Where to go tomorrow has not been decided. 明天到什么地方去尚未决定.
How to divide labor among the workers is still a question. 这些工人之间如何分工仍是个问题.
2. 作动词宾语：能够接"疑问词＋不定式"作宾语的动词常用的有advise, ask, consider, decide, discuss, explain, forget, know, learn, remember, show, teach, tell, wonder等.例如：
He has to learn how to collect water, hunt for food, and make fire. 他得学会收集淡水、寻找食物,生火什么的.
You should not go rafting unless you know how to swim, and you should always wear a life jacket. 如果不会游泳,就不要去做木筏漂流.漂流必须始终穿上救生衣.
3. 作双重宾语（宾语补足语）：某些动词后面可接"sb.＋疑问词＋不定式"构成的双重宾语,这类动词常用的有advise, ask, show, teach, tell等.例如：
He will advise you what to do. 他会建议你们做什么.
Will you show me how to use this machine? 你能示范教我如何使用这部机器吗?
4. 作介词宾语：某些介词后面可接"疑问词＋不定式"作宾语,这类介词常用的有 about, as, from, in, of, on, with等.例如：
You also need to learn the basic skills of rafting, such as how to handle the raft, how to paddle and how to get in and out of the raft. 你还需要学习基本划木筏的技巧,比如驾驭木筏的方法,划桨方法,上下木筏的方法.
He has no idea of how to answer this question. 他不知道怎样回答这个问题.
Della had only $1.87 with which to buy Jim a present. 德拉仅有$1.87为来吉姆买一件礼物.(which是关系代词)
You have a number of topics from which to choose. 你有很多题目可以选择.(which是关系代词)
5. 作表语
Perhaps the most difficult challenge is how to survive without friends. 也许最难熬的挑战,就是生活中孤独无友.
The question is which to choose. 问题是挑选哪一个.
6. 作状语
She was at a loss (as to) what to do. 她不知如何是好.
I have no idea which one to take. 我不知道拿哪个好.
7. 作同位语
The question whether to confess troubled the girl. 是否要坦白的问题使姑娘很烦恼.
He had no idea how to help the old man. 他不知道如何去帮助那位老人.
二、“特殊疑问词＋动词不定式”结构经常用在某些动词后作宾语,类似的动词有：tell, show, know, learn, teach, find out, forget, wonder, remember等.如：
I’ll show you how to do it. 我要让你看看如何做这件事.
You’d better find out where to put it. 你最好弄清楚要把它放在哪里.
三、“特殊疑问词＋动词不定式”这种结构可以把复合句转为简单句.如：
I don’t know what I’ll do next. = I don’t know what to do next.
The doctor told him when he should take the medicine. = The doctor told him when to take the medicine.
同样,因为“特殊疑问词＋动词不定式”这种结构相当于一个名词性从句,所以可用同等成分的从句代替,从而把简单句转换为复合句.改写时只需在疑问词后加上适当的主语,并把不定式改为适当的形式的谓语即可.如：
Li Ping doesn’t know why to learn English. = Li Ping doesn’t know why he should learn English.
Which to choose is important. = Which we should choose is important.
The question is where to go. = The question is where we should go.
四、“特殊疑问词＋动词不定式”这种结构可构成独立问句.如：
What to do? 怎么办?
How to get rid of the trouble? 如何摆脱困境?