noun clauses (名词从句)

有些从句，它们在句法上所起的作用与名词所起的作用是一样的。名词可以作主语、表语、宾语、介词宾语、同位语等，从句同样也可以作主语、表语、宾语、介词宾语、同位语等。名词从句(或名词性从句)就是为了反映这一句法特点而取名的。它是与形容词(性)从句、副词(性)从句相对而言的。名词(性)从句包括：

A. 主语从句

1. That he will help is certain. 他将进行帮助,这是肯定无疑的。

2. How the book will sell depends on the reviewers. 这本书的销售情况如何取决于评论家的评论。

3. Whether she likes the present is not clear to me. 她是否喜欢这件礼物，我还不清楚。

4. What he did is not yet known. 他干了什么事还不清楚。

5. When she'll be back depends much on the weather. 她什么时候回来主要取决于天气。

6. Whoever comes will be welcome. 谁来都会受到欢迎。

7. How a telephone works is a question which not everyone can answer. 电话是怎样工作的，这个问题并不是每个人都能回答出来的。

可以使用形式主语 it 来占据主语从句的位置,而使其退到主句之后:

1. It is strange that the children are so quiet. 真奇怪,孩子们那么安静。

2. It was clear enough what he meant. 他的意思够清楚的了。

3. It's really no business of yours where I spend my summer. 我在哪儿度暑假确实与你无关。

从上面的例句可以看出,除了连词 that, whether 之外,所有的 wh-词(what, who, which,when, where, why) 以及 how 也都能引导主语从句。if 不能引导前置的主语从句，但是却可以引导后置的主语从句，见 if $^{1-4}$ 。

B. 宾语从句

1. I noticed that he spoke English with an Australian accent. 我注意到他说英语带有澳大利亚口音。

2. He asked you whether you wanted to come in. 他问你是否想进来。

3. Tell me what you mean. 告诉我你什么意思。

4. I asked him who came into the room. 我问他谁进了房间。

5. I don't know who he's talking to. 我不知道他正在同谁谈话。

6. Ask him which he wants. 问他想要哪一个。

7. The driver asked me where I wanted to go. 司机问我想去哪儿。

8. I'll tell you why you have to study Shakespeare. 我将告诉你为什么必须研究莎士比亚。

9. I asked how he was getting on. 我问他近来情况怎样。

10. I asked her if she had any rooms to let. 我问她是否有房间出租。

11. I wonder whose house that is. 我想知道那是谁的房子。

从上面的例句可以看出,除了连词 that、whether、if 之外,所有的 wh-词以及 how 也都能引导宾语从句。还应注意的是,宾语从句有时可以前置:

1. That she ever said such a thing I simply don't believe. 她曾说过那样的事,我简直不能相信。

2. What would happen after that she could not imagine. 她不能设想在那之后会发生什么事。

3. Whether he's coming or not, I can't tell you. 他是不是来，我无法向你讲清楚。

可以使用 it 作形式宾语而使宾语从句退到主句之后，见 it $^{7-9}$ 。

C. 介词宾语从句：

1. He began to think about just what he would do. 他开始思考他要干什么。

2. It all depends on whether we can get their co-operation. 这都取决于我们能否得到他们的合作。

3. They did not consult us on whose names should be put forward. 他们没有问我们应把谁的名字排在前面。

4. It depends (on) whether you want to do it or not. 那要看你是不是愿意干这件事。

5. Write to who(m) ever you want. 请给你所需要的人写信。

D. 表语从句

除了连词 that、whether、as if、as though 之外，所有的 wh-词以及 how 也能引导表语从句：

1. The problem is who will water my plants when I am away. 问题是在我外出时谁将给我的植物浇水。

2. That was why he spoke French so funnily. 这就是为什么他说法语说得那么可笑的原因。

应当注意,与主语从句、宾语从句中的情形不同,if 不能引导表语从句(应改为 whether),但是 as if(as though)却可以引导下列连系动词的表语从句:be, seem, appear, chance:

It seems as if the weather is improving. 看来天气要变好。