实用英语语法精华班  
第22节 名词性从句之表语从句  
主讲人：徐国庆  
一、定义：表语从句只能置于主句之后，而主句的动词只能是  
连系动词。名词性从句在be动词等系动词后作表语时被称为表  
语从句。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。  
二、构成：主语+系动词+表语从句。  
三、引导表语从句的词：  
从属连词：that, whether, as though, as if  
连接代词：who, what, which, whom, whose, whatever,  
whoever, whomever, whichever等；  
连接副词：when, where, why, how, however,  
whenever, wherever等。  
由连接词that, whether引导的表语从句：  
that在引导表语从句时无词义，而whether有词义，意为“是否  
”
。这时主句的主语常常是些抽象名词，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。  
The question is whether we need more ice cream.问题是  
我们是否还需要一些冰淇淋。  
由连接代词引导的表语从句：  
连接代词who, what, which, whom, whose, whatever,  
whoever, whomever, whichever等引导表语从句，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。  
The problem was who could do the work.问题是谁能  
做这项工作。  
由连接副词引导的表语从句：  
连接副词 when, where, how, why 除在句子起连接作用外，  
在从句中还充当时间，地点，方式或原因状语，本身具有词  
义。例如：  
Go and get your coat. It's where you left it. 去把雨衣  
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.  
我们既没伞也没雨衣，这是我们淋湿的原因。  
That is how mice ruin many stores of grain every  
year.那就是老鼠是怎样每年损害大量粮食的  
由连词because, as if/as though等引导的表语从句：  
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。  
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除外，  
whether/if的区别详见宾语从句那一讲）  
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.区别于宾语从句，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。  
【
考点1】选择引导表语从句合适的连接词。  
1.连接词引导的表语从句  
that在引导表语从句时无词义，而whether有词义，意为“是  
否”，as if/ as though有词义，意为“好像，似乎”。  
例题1：She looked _________ she were ten years younger.  
A. that  
B. like  
C. as  
D. as though  
例题2：The most pleasant thing of the rainy season is  
one can be entirely free from dust.  
A. what  
B. that C. whether  
D. Why  
2.连接代词引导的表语从句  
连接代词who, what, which, whom, whose, whatever,  
whoever, whomever, whichever等引导表语从句，在句中作  
主语、宾语、表语，关系代词不能省略。  
例题1：The world is not always ______ we wish it to be.  
A. that  
where  
B. which  
C. what  
D.  
例题2：A ship in harbor is safe, but that’s not ______  
ships are built for.  
A. what B. whom C. why  
D. when  
3.连接副词引导的表语从句  
连接副词 when, where, how, why 除在句子起连接作用  
外，在从句中还充当时间，地点，方式或原因状语，本身  
具有词义。  
例题1：My job is very enjoyable. That is I spend a  
great deal of time and patience.  
A. what B. how  
C. when D. why  
【
考点2】because和reason在从句中的用法区别  
当主语是reason时，表语从句要用that引导而不是because，  
because在从句中充当副词性连词即引导状语从句。  
例题1：—I fell sick!  
-
-I think it is _______ you are doing too much.  
A.why B.when C.what  
D.because  
例题2：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  
【
“
考点3】That is why......及其相似结构  
That is why...”是常用句型， 意为“这就是...的原因/因  
此...”， 其中why引导的名词性从句在句中作表语， 该句型  
通常用于针对前面已经说明过的原因进行总结。如：  
That is why you see this old woman before you know,  
Jeanne. 珍妮， 这就是现在这个老太婆出现在你面前的原因。  
(
前文提到Jeanne对老妇人显得苍老憔悴深感诧异， 说话人  
对她讲述了其中的原因之后，用这一句来进行概括)。  
That is why I came. 这就是我来的原因。  
下面是两个与“That is why...”形式相似的结构， 它们与  
That is why...”结构之间的关系要能够辨析清楚：  
1)“That is why...”与“That is the reason why...”同义，  
“
(
只不过从语法结构上讲，“That is the reason why...”中why  
引导的是—个定语从句，将其中的the reason去掉则与“That  
is why...”结构一样，例如：  
That is (the reason) why I cannot agree. 这就是我不能同意  
的理由。  
(2)“That is because...”句型中从属连词because引导的名词性从句在此作  
表语，这也是个常用句型， 意为“这就是为什么.../因为...”。“That is  
because...”与“That is why...”之间的不同在于“That is because...”  
指原因  
或理由，“That is why...”则指由于各种原因所造成的后果，例如：  
He did not see the film last night. That is because he had to help his  
little  
sister with her homework.  
昨天晚上他没有去看电影， 那是因为他得帮助他的妹妹做作业。  
(
第一句话说明结果， 第二句话说明原因)  
He had seen the film before. That is why he did not see it last night.  
他以前曾看过那部电影，  
因此他昨天晚上没有去看。  
(
第一句话说明原因， 第二句话说明结果)  
例题1：I had neither a raincoat nor an umbrella ____I got wet  
through.  
A. It’s the reason B. That’s why C. There’s why  
D. It’s how