主语从句与先行it

发布时间:2017-12-23 编辑:互联网 手机版

深圳市宝安高级中学 顾永

主语从句可以按其引导词的不同分为三类:

第一类,用从属连词that引导的主语从句,例如:

That we shall be late is certain.

That the driver could not control his car was obvious.

这种结构主要是对that从句的内容进行强调,属正式文体,连词that不可以省略;但是在一般情况下,往往使用先行it结构,即用it作形式主语,而把that从句放到后面,这时,在口语中,连词that有时则可以省略。所以上述两句可以改为:

It is certain that we shall be late.

It was obvious that the driver could not control his car.

如果整个句子是疑问形式,就只能用先行it结构,例如:

Is it true that he would take the risk?

Is it possible that they will come tomorrow?

常使用先行it结构,用that从句作主语的句子有下列几个句型:

1、It + be + 形容词 + that从句:

It is clear that he was telling the truth.

It’s probable that we’ll be a little late.

2、It + be + 名词词组 + that从句:

It’s a pity that you can’t go with us.

3、It + 及物动词 + 宾语 + that从句:

It worried her a bit that her hair was turning grey.

It shocked me that Peter didn’t tell anybody where he was.

4、It + be + 过去分词 + that从句:

It is said that he has been there many times.

5、It + seem/happen/appear等不及物动词 + that从句:

It seems that he has lost something.

注意:

在上述第1和第2两种句型中,that从句前置与使用先行it,that从句后置在意义上没有什么差异;但使用先行it结构较为常见。

在第3种句型中,that从句前置在语法上是可能的,但实际上并不常见,通常总是使用先行it结构 。

第4种句型实质上是被动结构,由于that从句不可以位于句首作被动句的主语,所以只能使用先行it结构。

第5种句型已经形成了固定的搭配关系,that从句不能前置,只能使用先行it结构,不过,这种结构可以转换为带有不定式的简单句,例如:

It happened that I had no money with me that day.

→ I happened to have no money with me that day.

第二类,用连接代词who、whose、which、what,连接副词when、where、how、why,以及连词whether(或if)引导的主语从句,例如:

Who was responsible for the accident is not yet clear.

→ It is not yet clear who was responsible for the accident.

What he did is not yet known.

→ It is not yet known what he did.

Whether it is true remains a problem.

→ It remains a problem whether / if it is true.

从以上例句可以看出,这类主语从句可以直接放在句首作主语,也可以使用先行it结构,把主语从句放在后面,两种结构可以互换,意义上无差异,但用if引导主语从句时,只能采取先行it结构,也就是说if不可以引导置于句首的主语从句。

第三类,用what、whatever、where、wherever、whoever、whichever等代词引导的主语从句,例如:

What he said at the meeting encouraged everyone.

Whoever fails to see this will make a big blunder.

这类从句一般相当于带有定语从句所修饰的名词词组,即在结构上相当于一个名词加上一个定语从句,例如:

What he wants to buy is a ten-speed bicycle.

→ The thing that he wants to buy is a ten-speed bicycle.

Whoever breaks the law is sure to be punished.

→ Anyone who breaks the law is sure to be punished.

切记,这类主语从句不可以使用先行it结构。

上述第二类主语从句与第三类主语从句尽管在形式上十分相似,但实际上是不同的。第二类结构中用连接代/副词引导的从句系由特殊疑问句转化而来,以whether/if引导的从句系由一般疑问句转化而来,自然含有疑问的意味,例如:

When they will have the sports meet is still a question.

→ When will they have the sports meet?

Who he is doesn’t concern me.

→ Who is he?

Whether he will join us won’t make too much difference.

→ Will he join us?

而第三类结构中的主语从句则没有疑问的意味。

试比较下列各句:

① What caused the accident is a complete mystery.

② What caused the accident was a broken bottle.

③ What she looks like doesn’t matter.

④ What she’d like is a digital watch.

上述各句中尽管都有一个以what引导的主语从句,但其意义不尽相同;第①和③句中的主语从句系由“What caused the accident?”和“What does she look like?”转化而来,所以可以改成:

It is a complete mystery what caused the accident.

It doesn’t matter what she looks like.

第②④句中的主语从句含义分别为“The thing that caused the accident”和“The thing which she’d like”,所以不含疑问意味,因此不可以说:

It was a broken bottle what caused the accident.

It is a digital watch what she’d like.

但是可以说:

It was a broken bottle that caused the accident.

It is a digital watch that she’d like.

不过,这已不是主语从句,而是强调结构了。

(2006-12-7)