表语从句
表语从句（Predicative Clause）就是用一个句子作为表语。说明主语是什么，由名词、形容词或相当于名词或形容词的词或短语充当表语。
一、that，whether引导的表语从句
例句：
The trouble is that I have lost his address.
麻烦是我把他的地址丢了。
The question remains whether they will be able to help us.
问题还是他们能否帮我们。
二、wh-和because引导表语从句情况
连接代词who, whom, whose, what, which, whoever, whatever, whichever
连接副词where, when, how, why
例句：
That’s because he didn’t understand me.
那是因为他没有理解我。（That’s because…强调原因）
That’s why he got angry with me.
那正是他对我生气的原因。（That’s why…强调结果）
The problem is who we can get to replace her.
问题是我们能找到谁去替换她呢。
The question is how he did it.
问题是他是如何做此事的。
What I wonder is when he left.
我想知道他是何时离开的。
That’s what he wants.
那是他想要的。
This is where they once lived.
这就是他们曾经住过的地方。
三、as，as if，as though引导表语从句
例句：
He looked just as he had looked ten years before.
他看起来还与十年前一样。
It sounds as if someone is knocking at the door.
听起来好像有人在敲门。
重点
表语是用来说明主语的身份、性质、品性、特征和状态的，表语常由名词、形容词、副词、介词短语、不定式、动词的-ing、从句来充当，它常位于系动词（be, become, appear, seem, look, sound, feel, get, smell等词）之后。如果句子的表语也是由一个句子充当的，那么这个充当表语的句子就叫做表语从句。
难点
1. 表语从句一定要用正常语序。
False: The question is when can he arrive at the hotel.
Right: The question is when he can arrive at the hotel.
2. 引导名词性从句时if/whether（是否）用法辨析：
if不能引导表语从句，只能用whether 来引导。
引导宾语从句时if/whether可以互换，但介词后面的宾语从句只能用whether来引导。
位于句首的主语从句只能用whether来引导，同位语从句也只能用whether来引导。
False: The question is if the enemy is marching towards us.
Right: The question is whether the enemy is marching towards us.
易错点：
1. 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.
2. 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连系动词。名词性从句在be等系动词后作表语时被称为表语从句。
例如：
The problem is how we can get the things we need.
问题是我们怎样能弄到我们需要的东西。（how 在表语从句中充当方式状语）
The scissors are not what I need.
这把剪刀不是我所需要的。（what 在表语从句中充当宾语)
题模精讲
题模一 that，whether引导的表语从句
The traditional view is_________we sleep because our brain is “programmed” to make us do so.
A、when
B、why
C、whether
D、that
答案：D
解析：考查that引导的表语从句。下划线处之后是包含一个原因状语从句的表语从句，如果看不出它是充当整个句子结构的表语从句将难以把握整个句子的意思。因此应选择可引导名词性从句且不充当任何成分的that，故选D。
题模二 wh-和because引导表语从句情况
_________made the school proud was_________more than 90% of the students had been admitted to key universities.
A、What; because
B、What; that
C、That; what
D、That; because
答案：B
解析：考查表语从句。第一个下划线处的引导词引导主语从句并在该主语从句中充当主语，特指令校方骄傲的事情，应选用关系代词型的引导词what；第二个下划线处引导表语从句表示原因、理由，应由that引导对应的名词性从句，故选B。
题模三 as，as if，as though引导表语从句
Another man, lying on his side, looks_________he is trying to get up.
A、if
B、like
C、as if
D、that
答案：C
解析：考查as if引导的表语从句。lying on his side为分词短语作定语，补充说明another man，故选C。
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