我们都知道，在一个句子里面，每个词语都充当着重要的角色，如主语、宾语、补足语等。我们还知道，在英语里面，除了单词可以充当这些成分，一些句子也有同样的功效，它们被称为从句。那么今天，就让我们一起来看一下，表语从句是如何在句子里发挥它作为表语的功效的。
26.1表语从句概述
表语从句就是用一个句子作为表语，说明主语是什么或者怎么样，放在连系动词之后。
其结构是“主语+系动词+表语从句”。
26.2表语从句的引导词
表语从句的引导词有以下几类。
（1）从属连词：that， whether， as though， as if。
（2）关系代词：who， what， which， whom， whose， whatever， whoever， whomever， whichever等。
（3）关系副词：when， where， why， how， however， whenever， wherever 等。
可以接表语从句的连系动词有be， look， remain， seem 等。
26.3由从属连词引导的表语从句
that 在引导表语从句时无词义，也不充当成分。引导表语从句的that 通常不省略，但在口语或非正式文体中有时也可省略。而whether 有词义，意为“是否”。这时主句的主语常常是一些抽象名词，如question（问题），trouble（麻烦），problem（问题），result（结果），chance（可能性），suggestion（建议），idea（想法），reason（理由）等。表语从句对主句的主语进行说明、解释，使主语的内容具体化。例如：
The trouble is (that) she has lost his money.
麻烦的事是他丢了钱。
My idea is (that) we should do the task right away.
我的意见是我们应该马上开始这个任务。
The question is whether we need more help.
问题是我们是否还需要更多的帮助。
The problem was that it was too valuable for everyday use.
问题是它作为日常之用太贵重了。
26.4由关系代词引导的表语从句
关系代词who， what， which， whom， whose， whatever， whoever， whomever， whichever 等引导的表语从句，在句中作主语、宾语、表语，关系代词不能省略。例如：
The question is which of us should go.
问题是我们哪一个应该去。
That"s what he is worrying about.
那就是他在担心的事。
The problem is who we can get to replace her.
问题是我们能找到谁去替换她。
The question is who(m) we should trust.
问题是我们应当相信谁。
What I want to know is which road we should take.
我想知道的是我们应该走哪条路。
Dialogue & Analysis（此处有视频学习资料）
M： Most new fish come close to madness the first night.Somebody always breaks down crying.Happens every time.The only question is who is it going to be？
26.5由关系副词引导的表语从句
关系副词when， where， why， how， however， whenever， wherever 等能够引导表语从句，而关系副词 when， where， how， why 除在句子中起连接作用外， 在从句中还充当时间、地点、方式或原因状语，本身具有意义。例如：
Go and get your coat.It is where you left it.
去把外套拿来。就在你原来放的地方。
I had neither a raincoat nor an umbrella.That"s why I got wet through.
我们既没有伞，也没雨衣。这就是我们淋湿了的原因。
That is how mice ruin many stores of grain every year.
那就是老鼠如何每年损害大量粮食的。
That is what he is worried about.
那就是他所担心的。
26.6由连词because， as if/as though 等引导的表语从句
当然，除了上述词类之外，连词because，as if/as though 等也可以引导表语从句。例如：
It looked as if it was going to snow.
看起来好像要下雪了。
That"s because we never thought of it.
这是因为我们从未想过此事。
It seems as if he didn"t know the answer.
好像他不知道答案。
I.选择题。
1.The question is we will have our sports meet tomorrow.
A.that
B.if
C.when
D.whether
2.The reason why he failed is he was too careless.
A.because
B.that
C.for
D.because of
3.Go and get your coat.It"s you left it.
A.where
B.there
C.there where
D.where there
4.The problem is to take the place of Ted.
A.who can we get
B.what we can get
C.who we can get
D.that we can get
5.What I want to know is he likes the book given by Mary.
A.that
B.if
C.whether
D./
6.The reason is I missed the train.
A.that
B.when
C.why
D.what
7.That is we were late last time.
A.that
B.when
C.why
D.what
8.He looked he were ten years younger.
A.that
B.like
C.as
D.as though
9.- I feel sick！
- I think it is you are doing too much.
A.why
B.when
C.what
D.because
10.The reason why he hasn"t come is .
A.because his mother is ill
B.because of his mother"s being ill
C.that his mother is ill
D.for his mother is ill
11.- He was born here.
- That is he likes the place so much.
A.that
B.what
C.why
D.how
12.That is Lu Xun once lived.
A.what
B.where
C.that
D.why
II.选择题。（注意that和what 的区别）
1.your mother wants to know is getting on with your studies.
A.What；how are you
B.That；how you are
C.How；that you are
D.What；how you are
2.The trouble is we are short of tools.
A.what
B.that
C.how
D.why that
3.America was was first called “India” by Columbus.
A.what
B.where
C.the place
D.there where
4.Nowadays， China is becoming stronger and stronger.It is no longer .
A.what it used to be
B.what it was used to being
C.what it used to being
D.what it was used to be
5.he really means is he disagrees with us.
A.What；that
B.That；what
C.What；what
D.That；what
6.The energy is makes the cells able to do their work.
A.that
B.which
C.what
D.such
