(完整)高中英语主语从句全面讲解

语法——Noun clauses as the subject

主语从句

如果一个句子在复合句中充当一个主语, 那么这个句子就是主语从句。

①That he finished writing the composition in such a short time surprised us all.

②What we need are good doctors.

③Whom we must study for is a question of great importance.

1.主语从句的连接词

1).连接词: that, whether

①.That he will win is certain.

②.Whether he’ll join us in the discussion is of great importance.

2).连接代词: who, what, which, whom , whose, whoever, whatever, whichever

①.It is clear who is afraid of having a change in land ownership.

②.What India needs is a law to make land ownership fairer.

3).连接副词: when, where, why, how, how many, how much , how long, how soon, how often

①When we’ll start tomorrow will be told soon.

②Where we can buy oxen is something we need to find out.

③Why he came here is not known.

④How we can protect the grain from damp needs to be discussed.

【连接词】

1. that——That t he earth moves around the sun is well known.

2. whether——Whether he will come or not is not known yet.

3. who ——Who will be sent there has not been decided.

4. what——What you need is more practice.

5. which——Which one is the best is not clear.

6. when, where ——Where he has gone is a question.

7. why, how——Why there is gravity is hard to understand.

How he can earn a living in Britain remains a big problem.

8. whoever、whatever、whichever可引导主语从句。

Whoever comes will be welcome. Whatever he did was right. Whichever of you comes in will receive a prize. 【小结】

1. 引导主语从句连词有that, whether, who, what, whatever等。

2. 连词位于句首不能省略。

3. 主语从句大多数情况下视为第三人称单数, 但在连接代词what引导的主语从句后谓语动词的数要根据句意而定。

★为了防止句子头重脚轻，通常把形式主语it 放在主语位置，真正主语后置。

1. It is certain that he will win the match.

2. It is true that he has made a very important discovery in chemistry.

3. It is very likely that they will hold a meeting.

4. It is strange that the man should have stuck to his silly ideas.

5. It is a pity that we won't be able to go to the south to spend our summer vacation.

6. It is still a mystery what caused the accident.

7. It is said that he has gone to Shanghai.

8. It seems that he has seen the film.

【小结】

1.以that 引出的主语从句,常以形式主语it引导, 结构为：It is +形容词/名词/某些动词ed + that 从句。

2.在有些that从句中要用虚拟语气 (should +do/should +have done)。

★用it 作形式主语的结构

(1) It is ＋名词＋从句

It is a fact that …事实是…

It is an honor that …非常荣幸

It is common knowledge that …是常识

(2) It is ＋形容词＋从句

It is natural that…很自然…

It is strange that…奇怪的是…

(3) It ＋不及物动词＋从句

It seems that…似乎…

It happened that…碰巧…

It appears that…似乎…

(4) It ＋be+ 过去分词＋从句

It is reported that…据报道…

It has been proved that…已证实…

It is said that…据说…

★“It”作形式主语代替主语从句的常见句型举例

①It’s + adj. + that / wh- clause

e.g. It’s clear / natural / certain that clause

It’s obvious that money doesn’t grow on trees.

②It’s + p.p. + that / wh- clause

e.g. It’s said / reported / known that clause

It’s believed that he will come next week.

③It ‘s + n. + that / wh- clause

e.g. It’s a shame / an honour / good news that clause

It’s still a question when we’ll have our meeting.

④It + v. (n. / pron.) that /wh- clause

e.g. It made us very happy that she was chosen.

It appears that he forgot to sign the letter.

★whether与if均为“是否”，但下列情况下只用whether：

1. 引导主语从句并在句首——Whether he will come is not clear.

2. 引导表语从句——The question is whether he’ll come.

3. whether从句作介词宾语——I’m not sure about whether we’ll win.

4. 引导让步状语从句时——Whether you like it or not, you’ll have to do it.

【注意事项】

1. 主语从句位于句首时必须由连接词引导。