It is certain that she will do well in her exam. It is true that I told her everything.
It is said that Mr. Green has arrived in Beijing. It is reported that China has sent another manmade earth satellite into orbit.
2)连接代词who ，what ，which, whatever, whichever, whoever
充当成分，有具体意义
What seems easy to some people seems difficult to others. Which side will win is not clear.
主语从句常用it作形式主语放句首
因而我们常见到这种句式： It+be+n./adj/-ed从句（that,
whether,etc.) 例：It's a pity that you should have
to leave. = That you should have to leave is a pity. It is great that I have a teacher like you. = That I have a teacher like you is
注意:
1）主语从句在句首时，必须由连接词引导， 不能省略这些连接词；但是如果用it做形式 主语，而把主语从句放在句末时，从属连词 that可以省略。
4) . 用于It is important / natural / necessary / impossible that...句型中, 主语从句应使用虚 拟语气, 谓语动词用\“should + 动词原形\”的 形式, should有时可以省略。
“How do you do?” is a greeting. What she said is not yet known. That we shall be late is certain. It is certain that we shall be late.
主语从句 （Noun Clauses as the Subject）
It doesn’t matter whether she will come or not.
It makes no difference where we shall have the meeting.
3) It +及物动词（被动语态）+主语从句
It has been decided that the exhibition will not open on Sundays.
2.位置： 主语从句可以前置，也可以 后置。用it做形式主语，而把主语从 句，在句末，常用下面几种句型。
1）It + be + 表语 +主语从句 表语：（名词， 形容词，过去分词）
It is a fact (a shame, a pity, good news…) that…
It is still uncertain whether he is coming or not. It is an honour that I was invited to attend the meeting.
3)连接副词when，where， how， why等。
Why he did it remains a mystery. When they will start is not known yet. How he became a great scientist is known to us all.
Noun Clauses ---The subject clause
By Debby
Grammar
What part does the underlined part serve as in each sentence?
A tree has fallen across the road. You are a student. To find your way can be a problem. Smoking is bad for you.
定义： 用作主语的从句叫主语从句，它是名
词性从句之ቤተ መጻሕፍቲ ባይዱ。引导主语从句的连接词有：
连词that, whether；连接代词who, what和which；连接副词when, where, how和why。
主语从句的连接词
1.连词 that(无 词 义 , 不 作 成分 , 不 能 省 略);whether(是否),if不能位于句首。
5) 在It + be+suggested/advised/ordered/requested/ insisted/required 中, that从句的谓语也应 该用\“should + 动词原形\”的形式, should有 时可以省略。
3. 主语从句需注意的问题 (1)主语从句中用陈述语序 What she is afraid of is their taking her to Paris. ( What is she afraid of … Wrong ) (2)主语从句后谓语动词用三人称单数 That they haven’t phoned is strange.
2）It+不及物动词+主语从句 It seemed (happened, doesn’t matter, has turned out) that…
It happens that they were absent. It seems that Alice is not coming to the party at all.
2.That he will come and help us is certain. 3.Whether we will succeed is still a
question. 4.It is not known if he will come.
注意: 已确定的事由that引导; 没决定的事由whether引导.