高中英语必修3UNIT4 语法

高中英语必修3UNIT4 语法
高中英语必修3UNIT4 语法

高中英语必修3UNIT4 语法
主语从句
一、 名词性从句概述：
在句子中起名词作用的句子叫名词性从句(Noun Clauses）.名词性从句的功能相当于名词词组, 它在复合句中能担任主语、宾语、表语、同位语、介词宾语等,因此根据它在句中不同的语法功能,名词从句又可分别称为主语从句、宾语从句、表语从句和同位语从句.
名词性从句的连词
连接词：that,if/whether(是否),
连接代词：what, whatever, who, whoever, whom, whomever, whose, which, whichever
连接副词：when, where, how, why, whenever, wherever, however
二、主语从句的连词分三类
（1）从属连词引导的主语从句 （that whether if）
that引导的主语从句:引导词that无含义/在句中不做成分/不可以省.That 引导主语从句通常用it 作形式主语.
例如：That you will win the medal seems unlikely.
That you are so indifferent bothers me.
That she survived the accident is a miracle.
whether 引导的主语从句: whether有含义(是否)/在句中不做成分/不可以省.
注意：引导主语从句,不能用if不能在开头,只能用whether.
Whether we will hold a party in the open air tomorrow depends on the weather.
Whether she is coming or not doesn’t matter too much.
（2） 用连接代词引导的主语从句
在由连接代词who, whose, whom, which, what, whoever, whomever, whichever, whatever引导的名词性从句中,其连接代词在句中起名词性作用,担当一定成分.
例如：What you need is more practice.
What I want to know is this.
Whatever we do is to serve the people.
注：whatever / whoever的功用
whatever, whoever在主语从句中不含疑问意义.它引导主语从句,并在从句中作主语、宾语、表语等.
whatever = anything that; whoever = anyone who.要注意和whatever, whoever引导的让步状语从句的区别.
如：
Whoever breaks the law should be punished. （主语从句）
（ ＝Anyone who breaks the law should be punished. ）
Whoever breaks the law, he should be punished. （让步状语从句）
（ ＝No matter who breaks the law, he should be punished. ）
（3）用连接副词when, where, why, how引导的名词性从句(其连接副词有含义,在句中作状语.)
例如:Where we should leave it is a problem.
When they will come hasn’t been made pubic.
三、it 作形式主语的主语从句
有时为了考虑句子平衡,通常在主语从句处使用形式主语it,而将真正的主语从句移至句末.这分四种情况：
(1) 对于以连词that引导的主语从句,通常用形式主语it替代主语从句：
It is +名词+从句
It is a fact that… 事实是……
It is good news that … ……是好消息
It is a question that … ……是个问题
It is common knowledge that … ……是常识
类似的名词还有：a pity；a wonder；a good thing； no wonder； surprise等.
It is a mystery to me how it all happened.
It is common knowledge that the whale is not a fish.
It is no surprise that Bob should have won the game.
It’s a pity that you missed the film.
It is +形容词+从句
It is necessary that … 有必要……
It is clear that … 很清楚……
It is likely that … 很可能……
It is important that … 重要的是……
类似的形容词还有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite; unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc.
It is doubtful whether she will be able to come.
It was really astonishing that he refused to talk to you.
It is essential that he should be here by the weekend.
It seems obvious that we can not go on like this.
It is necessary that you （should）master the computer.
It is important that a student learn English well.
It’s clear that they badly need help.
It is likely that a hurricane will arrive soon.
需要注意的是,这类主语从句中,谓语动词很多为“（should）＋动词原形”,即要用虚拟语气.
It is +过去分词+从句
It is said that … 据说……
It is reported that … 据报道……
It has been proved that … 已证明……
It must be proved that… 必须指出……
类似的过去分词还有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc.
例如：It is thought that he is the best player.
It is estimated that the vase is 2000 years old.
It is used to be thought that a new star must be due to a collision between two stars.
It has not been made clear when the new road is to be opened to traffic.
It is said that he was killed in the earthquake.
It seems不及物动词 （happened / appears / doesn’t’t matter / makes no difference / occurred …）that …主语从句不可提前
It seems that they will win the game.
It makes no difference whether he will attend the meeting or not.
It does not matter if I missed my train.
It happened that I saw him yesterday.
(2) 对于以连接代词(副词)引导的主语从句,可以使用形式主语代主语从句,也可直接在句首使用主语从句：
Whether they would support us was a problem.
他们是否会支持我们还是一个问题.
It was a problem whether they would support us.
他们是否会支持我们还是一个问题.
It remains to be seen whether it will do us harm or good.
它对我们是利是害,还得看看再说.
(3) 对关系代词型what引导的主语从句,通常直接将主语从句放在句首.如：
What we need is money. 我们需要的是钱.
What I want to know is this. 我想知道的就是这一点.
有时也可将助用形式主语.如：
It is clear enough what he meant. 他是什么意思很清楚.
(4) 如果句子是疑问句,则必须用带形式主语it的结构：
Is it true that he is the girl’s father? 他是那女孩的父亲,是真的吗?
How is it that you are late again? 你怎么又迟到了?
四、连词that的省略问题
引导主语从句的连词that 有时可省,有时不能省,其原则是：若that引导的主语从句直接位于句首,则that不能省略；若that引导的主语从句位于句末,而在句首使用了形式主语it,则that可以省略：
That you didn’t go to the talk was a pity. 很遗憾你没去听报告.(that不可省)
It was a pity (that) you didn’t go to the talk. 很遗憾你没去听报告.(that可省)