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。 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： <a> 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. <b> 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。 <c> 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. <d> 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， that 不能省略； that 引导的主语从句位于句末， 则 若 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) 五、高考题： 1、 never occurred to me___you could succeed in persuading him to change his mind.(陕西高考) It A．which B．what C．that D．if
2、It's obvious to the students________they should get well prepared for their future.(天津卷) A．as B．that C．which D．whether
3、________some people regard as a drawback is seen as a plug by many others.(2010·北京) A．Whether B．What C．That D．How
4、It is uncertain________side effect the medicine will bring about，although about two thousand patients have taken it.(2010·浙江) A．that B．how C．what D．whether
主语从句练习题 1.________ makes mistakes must correct them. A. What B. That C. Whoever D. Whatever 2. It worried her a bit ____ her hair was turning grey. A. while B. that C. if D. for 3.When and why he came here ________ yet. A. is not known B. are not known C. has not known D. have not known 4. ________ is no reason for dismissing her. A. Because she was a few minutes late B. Owing to a few minutes late C. The fact that she was a few minutes late D. Being a few minutes late 5. ________ Tom liked to eat was different from ________. A. That…that you had expected B. What …that you had expected C. That…what you had expected D. What…what you had expected 6.________ we go swimming every day ________ us a lot of good. A. If...do B. That...do C. If...does D. That...does 7.It ________ Bob drives badly. A. thinks that B. is thought what C. thought that D. is thought that 8.It's uncertain ________ the experiment is worth doing. A. if B. that C. whether D. how 9.________ the boy didn't take medicine made his mother angry. A. That B. What C. How D. Which 10.____ we can't get seems better than ____ we have. A. What, what B. What, that C. That, that D. That, what 11.____ you don't like him is none of my business. A. What B. Who C. That D. Whether 12..____ we'll go camping tomorrow depends on the weather. A. If B. Whether C. That D. Where 13._________is going to do the job will be decided by the Party committee. A. That B. Why C. How D. Who 14._______we'll finish translating the book depends on the time. A. When B. Why C. What D. That 15.______he won't go there is clear to all of us. A. How B. What C. Why D. This 16.______the house will be built will be discussed at tomorrow's meeting. A. If B. Where C. That D. What 17. ._______you come or not is up to you. A. What B. If C. Why D. Whether 18.._______makes mistakes must correct them. A. Who B. Anyone C. Whoever D. Anybody 19.._______team will win the match is a matter of public concern. A. Which B. That C. If D. How 20..________leaves the room last ought to turn off the lights. A. Anyone B. The person C. Whoever D. Who 答案：高考题：CBBA 1~5 CBACD 6~10DDCAA 11~15 CBDAC 16~20 BDCAC