主语从句(Subject Clause)
定义: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.
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）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 has'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.
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单三,但也有例外,如例9
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）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)
小结:
（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.
表语从句
一 定义：
A 表语从句就是用一个句子作为表语。
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
B 连接表语从句的连接词有：that, what, who, when, where, which, why,
whether,how.
He has become a teacher.
He has become what he wanted to be ten years ago.
She has remained there for an hour.
She has remained where I stood yesterday for an hour.
His suggestion is good.
His suggestion is that we should stay calm.
The question is confusing.
The question is when he can arrive at the hotel.
who will travel with me to Beijing tomorrow.
why he cried yesterday.
how I can persuade her to join us in the party.
whether the enemy is marching towards us.
二 注意：
A 表语从句一定要用陈述语序。
False: The question is when can he arrive at the hotel.
Right: The question is when he can arrive at the hotel.
B 不可以用if，而用whether 连接表语从句(as if 例外）。
False: The question is if the enemy is marching towards us.
Right: The question is whether the enemy is marching towards us.
Right: It looked as if he had understood this question.
C 不像宾语从句，在有表语从句的复合句中，主句时态和从句时态可以不一致。
Right: The question is who will travel with me to Beijing tomorrow.
Right: The question is why he cried yesterday.
D that在表语从句中不可以省掉。
表语从句只能置于主句之后，而主句的动词只能是联系动词。
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