名词性从句之主语从句讲解

名词性从句---主语从句

1. What is needed for the space trip is careful preparation.

2. Her wish is that she can lose weight soon.

3. I think that woman can reach every high achievements in many fields of scienee.

4. We were very excited at the n ews that our team had won.

引导名词性从句的关联词可分为三类：

一•从属连词：that （无任何词意）

whether, if （均表示"是否"表明从句内容的不确定性）

as if ,as though （均表示"好像"，“似乎"）以上在从句中均不充当任何成分

二.连接代词：what, who, whom, which ，whose, whatever, whoever, whichever（作主宾表定）

三.连接副词：when, where, how, why（作状语）

I. 主语从句

1. 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。

2.

位置：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。

3. 引导主语从句的关联词：

（1）从属连词that,whether,if （在从句中不充当成分，仅起连接作用）

That Jack won the match yesterday surprised us.

Whether he' ll come heresn ' t clea（此处不能用if）

（2）连接代词who, whom, whose, what, which, whoever, whatever, whichever （充当主宾表定）

What she did is not known.

Whoever comes is welcome.

（3）连接副词where,when,how,why（在从句中充当状语）

How this happened is not clear to anyone.

When the meeting will be held is decided by our manager.

4. 有时为了避免头重脚轻，常用it作形式主语，而把真正主语放在句子末尾。

How the book will sell depends on its author.

=It depends on its author how the book will sell.

That he is the best stude nt in the class is obvious.

=It is obvious that he is the best stude nt in the class.

用it作形式主语的几种常见结构：

（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 com mon kno wledge that 是常识•

⑵It is +形容词 +从句

It is natural that 很自然It is strange that 奇怪的是…

⑶It is +不及物动词+从句

It seems that 似…乎•…It happe ned that 碰巧•…

It appears that 似乎…

⑷It +过去分词 +从句

It is reported that 据报道…It has bee n proved that 已证实•…

It is said that 据说•…

注意：主语从句不可位于句首的五种情况

(1) if引导的主语从句不可居于复合句句首。(例子见上面)

⑵It is said , (reported) 结构中的主语从句不可提前。

例如：It is said that Preside nt Xi will visit our school n ext week.

⑶It happens …，It occur结构中的主语从句不可提前。

例如：It occurred to him that he failed in the exam in ati on.

⑷It doesn ' t matter how/wheth结构中的主语从句不可提前。

例如：It doesn ' t matterhether he is wrong or not.

(5)含主语从句的复合句是疑问句时，主语从句不可提前。

例如：Is it likely that it will rain in the evening

5. 语序：主语从句用陈述语序。(关联词位于句首不能省略)

How he became a great scie ntist is known to us all.

Who the watch bel ongs to is unknown.

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

6. 主语从句中注意的事项：

1) 主语从句后的谓语动词一般用单数。

Whatever he says is of no importa nee.

Whoever says this is wrong.

但谓语动词用单数还是复数，不可一概而论，而要视句子的意义而定

What I n eed is mon ey.

What I n eed are books.

2) what与that在引导主语从句时的区别：

what引导主语从句时在从句中充当句子成分，如主语、宾语、表语，而that则不作任何成分。What you said yesterday is right.

That she is still alive is a consolation.

3) it作形式主语和it用于强调句的比较：