主要由两部分构成:疑问词和动词不定式(wh-+to do)。疑问词部分包括疑问代词who, whom, what, which和whose以及疑问副词when, where和how。此外,连接词“whether”也适用。主要具有以下几种功能:
⑴当主语
● When to hold the meeting has not yet been decided.
● Where to live is a problem.
⑵当宾语
常接在forget, find out, discuss, decide, tell, teach, know, learn, wonder, remember等动词之后作宾语如:
● We must know what to say at a meeting.
● He could not tell whom to trust.
● Do you know how to play bridge?
⑶当表语
● The problem is where to find the financial aid.
● The question is who to elect.
⑷当名词同位语
● Tom had no idea which book to read first.
● The question whether to confess troubled the girl.
⑸用于宾语补足语,双重宾语
某些动词后可接“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
● I can tell you where to get this book.
● I ask her how to learn English.
● He will advise you what to do.
● Will you show me how to use the machine?
(6) 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:
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)
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:
Which to choose is important. = Which we should choose is important.
The question is where to go. = The question is where we should go.
比如:
What to do? 怎么办?
How to get rid of the trouble? 如何摆脱困境?
按照英语语法的习惯,疑问副词why 后不直接跟动词不定式,如:
误:I don’t know why to choose that dictionary.
正:I don’t know why you must choose that dictionary.
但它可以接不带to的动词不定式,即动词原形,构成why do sth./ why not do sth. 肯定形式是表示某动作是不必要的或没有意义的,而否定形式是表示向某人提建议和表达看法,相当于祈使句。
Today is Sunday. Why not go out to relax yourself?
Why pay more at other shops? We have the best value.
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