语法知识复习

主语从句(Subject Clause)

定义:在复合句中充当主语的句子叫做主语从句.

第一部分：常规主语从句，即句子在复合句中充当一个主语

（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三单,但也有例外,如例9

（4）主语从句的时态：不受主句的时态影响和限制。

例句：

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

（2）Whether we will go for an outing tomorrow remains unknown.

（3）Who will be our monitor hasn't been decided yet.

（4）Whom we must study for is a question of great importance.

（5）What caused the accident remains unknown.

（6）Whatever you did is right.

（7）Whose watch was lost is unknown. （8）What we need is time.

（9）What we need are good doctors.

第二部分：为了防止句子头重脚轻，通常把形式主语it放在主语位置，真正主语搁置于句末

（1)以that 引出的主语从句,常以形式主语it引导. 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)例句4,5,6,11. 例句：

（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 he should do that. （5）It is important that we all should attend the meeting.

（6）It is strange that the man should have stuck to his silly ideas.

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

（8）It is still a mystery what caused the accident.

（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai)

（10）It is known to all that the gun powder was first invented by the Chinese. （11）It is suggested that the work should be done with great care.

（12）It seems that he has seen the film.(=He seems to have seen the film)

（13）It happened that the two cheats were there. (=The two cheats happened to be there)

第三部分：It 作形式主语和it引导强调句的比较

It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如：

It is a pity that you didn’t go to see the film.

表语从句

1. 定义：表语从句就是用一个句子作为表语。位于系动词之后，说明主语身份，特征，属性或状态。

比较：

The problem is puzzling.

主语连系动词形容词作表语

The problem is when we can get a pay rise.

主语连系动词一个句子作表语---表语从句

2. 系动词的分类（了解哪些词为系动词）

系动词有表示状态的；有表示状态变化的。

表示状态的有：

1）be, seem ,appear 等。

2）look ,sound ,feel ,taste ,smell 等，由感官动词变化而来。意思为“看（听、摸、尝、闻）起来”。

Mr. Li looks quite young. 李先生看起来很年轻。

3）stand ,keep ,prove ,remain 等由不及物动词转化而来。

The machine has been standing idle. 这台

机器一直闲着不用。

4）表示状态变化的：become ,get ,grow, fall, turn等

He has fallen ill. 他已经病倒了。

三连接表语从句与主句的关系词主要有三类：

1. 从属连词：that（无有词义）, whether （是否,if （是否）