主语从句讲解与练习

主语从句

一、概述：在句子中起名词作用的各种从句统称为名词性从句。根据它们在句中的语法作用，这类从句又可分为主语从句、同位语从句、表语从句和宾语从句。 二.主语从句主要有三类：

（1） 由连词that引导的主语从句:引导词that无含义,在句中不做成分,不可以省。

例如：That you will win the medal seems unlikely. 你想获得奖牌看起来是不可能的。

That you are so indifferent bothers me. 你如此冷淡使我很烦恼。

That she survived the accident is a miracle. 她在事故中幸免于难简直是奇迹。

（2） 用连词 whether 引导的主语从句:whether有含义(是否),在句中不做成分,不可以省。

例如：Whether she is coming or not doesn’t matter too much. 她来不来都无关紧要。

（3） 用连接代词引导的主语从句(在由连接代词who, whose, whom, which, what, whoever, whomever, whichever, whatever引导的名词性从句中，其连接代词在句中起名词性作用，担当一定成分). 例如：What you need is more practice. 你所需要的是更多的训练。

What I want to know is this. 我想知道的就是这事。 Whatever we do is to serve the people. 我们无论做什么都是为人民服务。

（4）用连接副词when, where, why, how引导的名词性从句(其连接副词有含义,在句中作状语。)

eg:Where we should leave it is a problem.

When they will come hasn’t been made pubic. 他们什么时候来还不知道。 三.注意点:

1.it 做形式主语,而将主语从句放在句末（尤其是当谓语较短时）。 例如：That light travels in straight lines is known to all. 光沿直线传播，这是众所周知的事。

=It is known to all that light travels in straight lines. 众所周知光沿直线传播。

When the plane is to take off has not been announced . 飞机何时起飞还没有宣布。

= It has not been announced when the plane is to take off. 还没有宣布飞机何时起飞。

(当what引导的主语从句表示“?的东西”时，一般不用it作形式主语。) 错:It is a book what he wants.

对:What he wants is a book. 他想要的是本书。

例如：Has it been settled who will be sent to carry out the task ? 谁将被派去执行这项任务决定了吗 ？ 固定用法和译法

（1） It is +名词+从句

It is a fact that? 事实是?? It is good news that ? ??是好消息 It is a question that ? ??是个问题 It is common knowledge that ? ??是常识

类似的名词还有：a pity；a wonder；a good thing； no wonder； surprise等。

例如：It is a mystery to me how it all happened. 这一切是怎么发生的是个谜。

It is common knowledge that the whale is not a fish.

鲸鱼不是鱼，这是常识。

It is no surprise that Bob should have won the game. 鲍勃会赢得这场比赛，这不足为奇。 （2） It is +形容词+从句

It is necessary that ? 有必要?? It is clear that ? 很清楚?? It is likely that ? 很可能?? It is important that ? 重要的是??

类似的形容词还有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite; unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc.

例如：It is obvious that conductors and insulators are both important in industry.

很明显导体和绝缘体在工业中都很重要。

It is doubtful whether she will be able to come. 她是否能来令人怀疑。

It was really astonishing that he refused to talk to you . 他拒绝和你说话真是令人惊讶。

It is essential that he should be here by the weekend . 周末之前，他应该到这里是必要的。

It seems obvious that we can not go on like this. 很明显我们不能这样下去了。 （3） It is +过去分词+从句 It is said that ? 据说?? It is reported that ? 据报道?? It has been proved that ? 已证明?? It must be proved that? 必须指出??

类似的过去分词还有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear;

found out,etc.

例如：It is thought that he is the best player. 大家都认为他是最好的选手。

It is estimated that the vase is 2000 years old. 据估计这个花瓶有2000年的历史。

It is used to be thought that a new star must be due to a collision between two stars. 过去一直认为新星是由于两颗星星之间碰撞产生的。

It has not been made clear when the new road is to be opened to traffic. 还没弄清楚这条路将开始通车。

It does not matter if I missed my train, because there is another later. 没有赶上这趟火车没有关系，稍晚还有一趟。 It happened that I saw him yesterday. 碰巧我昨天看见他了。

当“及物动词 + 宾语”较短时，也可用这种结构。

例如：It shocked me that Peter did not tell anybody where he was. 让我吃惊的是彼得没有告诉任何人他在哪里。 It does not interest me whether you go or not. 我对你去不去不感兴趣。

2.只用whether不用if引导主语从句.

二、主语从句与形式主语it

有时为了考虑句子平衡，通常在主语从句处使用形式主语it，而将真正的主语从句移至句末。这分三种情况：

(1) 对于以连词that引导的主语从句，通常用形式主语代主语从句： It’s a pity that he didn’t come. 很遗憾他没来。

It is important that he should know about this. 他必须知道此事。 It’s vital that we be present. 我们出席是至关重要的。

It was intended that you be the candidate. 大家的意图是让你当候选人。 It is important that this mission not fail. 这项使命不失败至关重要。

It is essential that a meeting be convened this week. 本周开一次会非常重要。 It is appropriate that this tax be abolished. 废除这个税是恰当的。

It’s unfair that so many people should lose their jobs. 竟有这么多人失业这是不公平的。

It’s amazing that she should have said nothing about it. 她竟未谈及此事令人惊讶。

It’s unthinkable that they should deny my request. 他们竟然拒绝我的请求，这是不可思议的。

That they should refuse to sign the petition required great courage. 他们拒绝在请愿书上签字这是需要很大勇气的。

(2) 对于以连接代词(副词)引导的主语从句，可以使用形式主语代主语从句，也可直接在句首使用主语从句：

Whether they would support us was a problem. 他们是否会支持我们还是一个问题。

It was a problem whether they would support us. 他们是否会支持我们还是一个问题。

It remains to be seen whether it will do us harm or good. 它对我们是利是害，还得看看再说。

(3) 对关系代词型what引导的主语从句，通常直接将主语从句放在句首。如：

What we need is money. 我们需要的是钱。

What I want to know is this. 我想知道的就是这一点。 有时也可将助用形式主语。如：

It is clear enough what he meant. 他是什么意思很清楚。 (4) 如果句子是疑问句，则必须用带形式主语it的结构： Is it true that he is the girl’s father? 他是那女孩的父亲，是真的吗？ How is it that you are late again? 你怎么又迟到了？(from www.yygrammar 三、连词that的省略问题

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