主语从句和同位语.doc

主语从句
一、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 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/不可以省略。
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.
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 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 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.
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 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 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 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。
(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)

同位语从句
一、理解同位语从句的含义，把握同位语从句的实质
　　在主从复合句中作同位语的从句称为同位语从句。同位语从句一般用that, whether，what, which, who, when, where, why, how 等词引导，常放在fact, news, idea, truth, hope, problem, information, wish,promise, answer, evidence, report, explanation, suggestion, conclusion等抽象名词后面，说明该名词的具体内容。换言之，同位语从句和所修饰的名词在内容上为同一关系，对其内容作进一步说明。
例：The news that they had won the game soon spread over the whole school.他们比赛获胜的消息很快传遍了整个学校。
析：they had won the game说明The news的全部内容，因此该句为同位语从句。

二、正确运用同位语从句的引导词，准确把握同位语从句
1.如同位语从句意义完整，应用that引导同位语从句。（即that 不充当任何成分，只起连接作用，不可省略）
　　例：The general gave the order that the soldiers should cross the river at once.将军下达了战士们立即过河的命令。
　　析：the soldiers should cross the river at once是the order的全部内容，且意义完整，因此应用that引导同位语从句。
2.如同位语从句意义不完整，需增加"是否"的含义，应用whether引导同位语从句。（if不能引导同位语从句）
　　例：We'll discuss the problem whether the sports meeting will be held on time.我们将讨论运动会是否会如期举行的问题。
　　析：the sports meeting will be held on time意义不完整，应加"是否"的含义才能表达the problem的全部内容，因此应用whether引导同位语从句。
3.如同位语从句意义不完整，需增加"什么时候"、"什么地点"、"什么方式"等含义，应用when, where, how等词引导同位语从句。
　　例1：I have no idea when he will be back.
　　析：he will be back意义不完整，应加"什么时候"的含义才能表达idea的全部内容，因此应用when引导同位语从句。
　　例2：I have no impression how he went home, perhaps by bike.
析：he went home意义不完整，应加"如何"的含义才能表达impression的全部内容，因此应用how引导同位语从句。
4.当主句的谓语较短，而同位语从句较长时，同位语从句常后置。
如：The thought came to him that maybe the enemy had fled the city.    

三、把握同位语从句和定语从句的区别，明确同位语从句和相似从句的界限
同位语从句和定语从句相似，都放在某一名词或代词后面，但同位语从句不同于定语从句。同位语从句对名词加以补充说明，是名词全部内容的体现，且名词和同位语从句的引导词均不在从句中作成分；定语从句说明先行词的性质与特征，与先行词是修饰与被修饰的关系，且名词和定语从句的引导词均在从句中作成分。
区分时可以在先行词与与从句之间加一个系动词be,使之构成一个新句子，如果句子通顺且符合逻辑，则为同位语从句，反之，则为定语从句。
如：The report that he was going to resign was false.
因为the report was that he was going to resign 句意通顺，所以，that he was going to resign 是同位语从句。
例1：
1）Information has been put forward ____ more middle school graduates will be admitted into universities.
　　A. while    B. that    C. when    D. as
　　析：答案为B。more middle school graduates will be admitted into universities是Information的内容，且Information不在从句中作成分，所以该句为同位语从句。应将该句区别于：
2）It is said that more middle school graduates will be admitted into universities，this is the information ____ has been put forward.
　　A. what    B. that    C. when    D. as
　　析：答案为B。that has been put forward为information的修饰性定语，且information在从句中作主语，所以该句为定语从句。
例2：She heard a terrible noise,____ brought her heart into her mouth.
　　A. it B. which    C. this    D. that
　　析：答案为B。分析语境含义、句子结构和句子成分可知，该句为非限制性定语从句，先行词为a terrible noise，且它在从句中作主语。应将该句区别于：
　　I can't stand the terrible noise ____ she is crying loudly.
　　A. it B. which    C. this    D. that
析：答案为D。she is crying loudly是the terrible noise的内容，且the terrible noise不在从句中作成分，所以该句为同位语从句。

同位语从句和定语从句的三点区别
同位语从句和定语从句很相似,但还是有区别的,区别主要在以下三方面:
1. 从词类上区别
同位语从句前面的名词只能是idea,fact,news,hope,belief,suggestion,proposal,word,thought,doubt,truth,possibility,promise,order等有一定内涵的名词?而定语从句的先行词可以是名词?代词?主句的一部分或是整个主句?
如:The possibility that the majority of the labour force will work at home is often discussed. (同位语从句)
We are not looking into the question whether he is worth trusting.
(同位语从句)
Word came that he had been abroad. (同位语从句)
Our team has won the game, which made us very happy.
我们的队赢了,这让我们很高兴?(定语从句)
The doctor whom you are looking for is in the room.
你找的那位医生在房间里面?(定语从句)
His mother did all she could to help him with his study.他妈妈尽她的最大努力帮助他的学习?(定语从句,代词all作先行词?)
2. 从性质上区别
定语从句是从句对其先行词的修饰或限制,属于形容词性从句的范畴;而同位语从句是从句对前面抽象名词的进一步的说明和解释,属于名词性从句的范畴。如:
The news that our team has won the game was true. 我们队赢了那场比赛的消息是真的?(同位语从句,补充说明news到底是一个什么消息)
The news that he told me yesterday was true. 昨天他告诉我的那个消息是真的?(定语从句,news在从句中作told的宾语)
I made a promise that if anyone set me free I would make him very rich. 我许诺如果谁让我自由,我就让他非常富有?(同位语从句,补充说明promise到底是一个什么诺言)
The mother made a promise that pleased all her children. 妈妈做出了一个令她的孩子们高兴的许诺?(定语从句,promise在从句中作pleased的主语?)
3. 从引导词及其在句子中的成分上区别
有些引导词如how, whether, what可以引导同位语从句,但不能引导定语从句?如:
That question whether we need it has not been considered. 我们是否需要它这个问题还没有考虑?(同位语从句)
I have no idea what has happened to him. 我不知道他发生了什么事?(同位语从句)
引导词that引导定语从句时,在从句中一般作主语或宾语(指物时还可以用which代替),并且作宾语时常常省略?that在同位语从句中仅起连接作用,不充当任何成分,并且不能省略,也不能用which来代替?如:
The order that we should send a few people to help the other groups was received yesterday. 我们应派几个人去帮别的几个小组的命令昨天收到了?(同位语从句,是对order的具体解释,that虽不作成分,但不能省略?)
The order that we received yesterday was that we should send a few people to help the other groups. 我们昨天收到的命令是我们应该派几个人去帮助别的几个小组?(定语从句,是名词order的修饰语,that在从句中作received的宾语,可以省略)