表语从句

表语从句

一、表语
1．概念：表语一般位于系动词(如be，become，get，look，grow，turn，seem等)之后，用以说明主语的身份、特征和状态。
2．充当表语的词、短语或句子：一般由名词、名词性代词、形容词、分词、数词、不定式(短语)、动名词、介词短语、副词及表语从句等充当。
The cultural background of China is totally different from that of the US.(形容词作表语)
中国的文化背景与美国完全不同。
My suggestion is that we should start at once.(从句作表语)
我的建议是我们应该马上开始。
二、表语从句
在句子中起表语作用的从句称为表语从句。 从句也是句子，符合5种基本句型或there be 句型。引导表语语从句的连接词主要有: 从属连词、连接代词和连接副词。
1. 表语从句的连接词
(1)从属连词that和whether: 在从句中不作成分, that无实义，whether有“是否”之意, 均不能省略。
The reason (for your mistake) is that you lack confidence. 你犯错误的原因是你缺乏自信。
The question is whether we can reduce the cost of the product.
问题是我们能否降低产品的成本。
The reason for your mistake is that you lack confidence in yourself.
你犯错误的原因是你对自己缺乏信心。
The problem is whether the air pollution can be controlled. 问题是空气污染能否被控制住。
知识拓展
    一般不能用if引导表语从句，常用whether代替。
(2)连接代词: who, whom, whose, what, which, whoever, whomever, whatever, whichever 等。
This place isn’t what it used to be. 这个地方不是原来的样子了。
The doubt is who has got away with the document. 疑点就是谁拿走了文件。
I’d like to start my own business—that’s what I’d do if I had the money.
我愿意自己创业——那就是如果我有钱将会做的事情。
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。   
That was what she did this morning on reaching the attic. 那就是她今晨上了阁楼干的。
(3 )连接副词：when, where, why, how, whenever, wherever, however 。
The last time (we had great fun) was when we were visiting the Water Park.
我们上一次痛快地玩耍是我们 参观水上公园的时候。
[Why] not try your luck [downtown]? That’s where the best jobs are.
为什么不去市中心碰碰运气呢？那里有最好的工作。
That was where we camped last time. 那就是我们上次野营的地方。
That’s why he got angry with me. 那正是他对我生气的原因。
温馨提示
    where引导的表语从句有时含有引申意义，即表示 “在某一点上”。
--The mother tries to do everything for her son. 这位母亲尽力为她儿子做任何事情。
--That’s where she’s mistaken. 那就是她不对的地方了。
(4)其他连接词:because, as if, as though。
[From space], the earth looks blue. This is because about seventy-one percent of its surface is covered with water.从太空看, 地球是蓝色的。这是因为地球大约71%的表面都被水覆盖着。
It sounds as if you are from the south of the United States. 听起来你好像来自美国南部。
温馨提示
as if/though引导的表语从句，有时可用虚拟语气。
The thick smog covered the whole city. It was as if/ though a great black blanket had been thrown over it. 厚重的烟雾覆盖着整座城市，好像一个厚厚的黑色毯子扔到它的上面。
because，why引导的表语从句。
He failed.That is because he didn’t work hard. 他失败了。那是因为他没有努力工作。
2. 其他连系动词+表语从句
    除be以外，可用于表语从句的连系动词有: look, sound, taste, feel, remain等。
It looks as if it is going to be fine. 看来天要晴了。
3. 表语从句中需要注意的问题
(1)主语为名词reason时，表语从句中的连接词要用 that,不用 because，构成句型“The reason ( why...) is that....
The reason is that you haven’t been well prepared for what’s going to happen. 原因是你没有为将要发生的事作好准备。
The reason (why he came late) was that he got up late. 他来得晚是因为起床晚了。（句中why引导的是定语从句）
(2)表语从句中的虚拟语气
    如果主句的主语是advice，proposal，recommendation ,suggestion, order, command, request, requirement 等名词时, 表语从句的谓语应用虚拟语气，即无论主语是单数或复数，谓语一律用“ (should+)动词原形”的形式。
The proposal of the UN is that a peace-keeping force (should) be sent to the area.
联合国的建议是向这个地区派驻维和部队。
(3)常见句型: A is to B what C is to D. A对于B就像C对于D —样。
Engines are to machines [what hearts are to animals].
发动机对于机器犹如心脏对于动物一样。
例1 One reason for her preference for city life is _______ she can have easy access to places like shops and restaurants.
A. that        B. how        C. what         D. why
解析 句意: 她偏爱城市生活的原因之一是在城市里可以很容易找到像商店和餐馆之类的地方。系动词is之后是一个表语从句，而从句的结构完整，不缺任何成分,所以用that引导。
答案 A
例2 A ship in harbor is safe，but that’s not ________ ships are built for.
解析 句意：在港口的船是安全的,但是那并不是船被建造的目的。“ships are built for”为表语从句，该句中缺少宾语且表示“事物”，故答案为what。
答案what
例3 The problem is ________ we can improve our reading skills in such a short time.
解析 句意: 问题是我们如何是否能在这么短的时间内提升阅读技能。考查表语从句。根据句意填 how/whether。
答案how/whether
例4 一When we are choosing furniture, you only focus on function while I think more about the design.
—That’s ________ we differ.
解析 句意:——在选择家具时,你只注重功能而我更注重设计。——那正是我们不同的地方。考查表语从句。where在从句中作状语。
答案where