主语从句定义：在句子中担当主语的是一个从句，这个从句就叫做主语从句。
主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。
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。
That you will win the medal ems unlikely.
That you are so indifferent bothers me.
That she survived the accident is a miracle.
（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。
Whether she is coming or not doesn’t matter too much.
（3） 用连接代词引导的主语从句(在由连接代词who, who, whom, which, what, whoeve
r, 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).
中国黄土What you need is more practice.
What I want to know is this.
Whatever we do is to rve the people.
（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.
ATTENTION
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.
=It is known to all that light travels in straight lines.
When the plane is to take off has not been announced .
= It has not been announced when the plane is to take off.cad界面
(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。)
What he wants is a book. 他想要的是本书。
Has it been ttled who will be nt to carry out the task
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 … ……是常识双溪漂流
类似的名词还有：a pity；a wonder；a good thing； no wonder； surpri等。
例如：It is a mystery to me how it all happened.
It is common knowledge that the whale is not a fish.
It is no surpri that Bob should have won the game.
（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……
梦见雪山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.
It is obvious that conductors and insulators are both important in industry.
It is doubtful whether she will be able to come.
It was really astonishing that he refud to talk to you .
It is esntial that he should be here by the weekend .
It ems obvious that we can not go on like this.
（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; discusd; required; decided; suggested; demanded; made clear; found out,etc.
It is thought that he is the best player.
It is estimated that the va is 2000 years old.
It is ud to be thought that a new star must be due to a collision between two stars.
It has not been made clear when the new road is to be opened to traffic.
It does not matter if I misd my train, becau there is another later.
It happened that I saw him yesterday.
当“及物动词 + 宾语”较短时，也可用这种结构。
It shocked me that Peter did not tell anybody where he was.
It does not interest me whether you go or not.
2.只用whether不用if引导主语从句.
主语从句三要点
请观察下列句子，注意划线部分句子的意义及用法。
1. What surprid me most was that the little girl could play the violin so well.
2. Who will go to the concert is not known.
3. That she was chon made us very happy.
4. Whether she will come or not is still a question.
5. Which book they will choo is still unknown.
6. When we shall hold our sports meet is not decided.
7. It’s strange that he knows nothing about it.
年收入多少算小康
8. It is a pity that she has made such a mistake.
9. It is said that President Jingo will visit our school next week.
[小结归纳]
(一)语序
主语从句使用陈述语序，其通常结构为“引导词 + 主语 + 谓语 + 其他成分”；但当连接代词同时充当从句主语时，其结构为“连接代词 + 谓语 + 其他成分”，如句1、2。
(二)引导词万物皆有灵性
① that引导主语从句时无词义，也不充当任何成分，但通常不可以省略，如句3；
② whether引导主语从句时意为“是否”，通常不能用if来代替,如句4；
③ 可以引导主语从句的连接代词主要有：who, whom, who, what, which, whatever, whoever等，如句5；
④ 可以引导主语从句的连接副词主要有：where, when, how, why等，如句6。
(三)常见句型
有时为避免句子头重脚轻，常用it作形式主语，代替主语从句放在句首，而把主语从句置于句末。常用句型如下：小学生卫生手抄报
① It + be + 形容词 + that 从句， 如句7;
黑枸杞泡酒② It + be + 名词 + that 从句， 如句8;
③ It + be + 动词的过去分词 + that 从句， 如句9。
[即学即用]
I. 用适当的词填空，使句子意思完整。
1. ______ he didn’t attend the meeting yesterday wasn’t quite clear.
2. The Foreign Minister said, “It is our hope ______ the two sides will work towards peac
e.”
3. ______ team will win the match is still unknown.
4. ______ comes to the party will receive a prent.
5. ______ Mary has left is still a question.
6. It’s reported ______ three people were killed in the accident and five were hurt badly.
7. ______ he solved the problem successfully interested all of us.
