名词性从句之主语从句一、名词性从句概述：在句子中起名词作用的各种从句统称为名词性从句。

根据它们在句中的语法作用，这类从句又可分为主语从句、同位语从句、表语从句和宾语从句。

二、主语从句定义：在句中起主语作用的从句称为主语从句。

引导主语从句的连接词主要有：单纯连词（that, whether/ if）、连接代词(what, whatever, who, whoever, whom, whose, which, whichever等)和连接副词(when, where, why, how, whenever, wherever, however等)。

1)that引导的主语从句（1）由连词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。

例如：That you will win the medal seems unlikely.你能得奖看起来不大可能。

That light travels in straight lines is known to all. 众所周知，光沿直线传播。

That you don’t like him is none of my business.你不喜欢他不管我的事。

（2）形式主语it替代主语从句位于句首，that引导真正的主语从句会放到句子的后面。

常用的句式主要有如下几种：1.It+ 系动词+形容词+that从句。

如：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.例如：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.知识拓展：在“It is necessary / important/surprising/strange/unthinkable/unbelievable/incredible+that 从句”这类主语从句结构中，从句中谓语动词常用“（should）＋动词原形”，形式，即要用虚拟语气,should 可省略。

例如：It is necessary that a college student (should ) master one or two foreign languages. 大学生掌握一两门外语是有必要的。

It is strange that you (should) trust Jane.很奇怪你竟然相信简。

另外，需要注意的是，it作形式主语代替主语从句时，要注意和as引导的定语从句的区别。

试比较：It was reported that the US was under the terrorist attack.As was reported, the US was under the terrorist attack.（2）常见用it作形式主语的复合句结构2. It +系动词+名词+ that从句如：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。

例如：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.3. It +be +动词的过去分词+that从句如: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 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.4.It+特殊词+that从句。

如：It seems （happened / appears / doesn’t matter / makes no difference / occurred …）that …如：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) 用连词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，只能用whether。

例如：Whether you like him or not is none of my business.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.3) 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. ）4）用连接副词引导的主语从句用连接副词when, where, why, how, whenever, wherever, however等引导的主语从句从句(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.温馨提示：如果主语从句是由连接代词what, whatever, whoever等引导的，表示的是一个具体的东西或人时，这样的主语从句不能用it作形式主语。

What is worth doing is worth doing well.Whatever was said here has left us much too think.Whoever comes will be welcome.1）随堂练习1. It doesn’t matter _________ you turn right or left at the crossing---both roads leadto the park.A. whetherB. howC. ifD. when2. It suddenly occurred to him ________ he had left his keys in the office.A. whetherB. whereC. whichD. that3. ---- We’ve only got this small bookcase. Will that do?---- No, _________ I am looking for is something much bigger and stronger.A. whoB. thatC. whatD. which4. It doesn’t matter ________ you pay by cash or credit card in this store.A. howB. whetherC. whatD. why5. ________ the polluting factory will be removed from the city is, in fact, ________ the citizens are glad to see.A. That; asB. As; whatC. That; whatD. What; that6. I don’t say I am against Jackie’s plan. But the problem is ___________he does from the serious disease soon.A. what thatB. that whatC. whether whatD. what whether7. “When ________ leave for Japan?”“When _______ leave for Japan is kept secret.”A. they will; will theyB. will they; they willC. they will; they willD. will they; will they8. They lost their way in the forest, and _________ made matters worse was that night began to fall.A. itB. whichC. thatD. what9. It has come to my notice ________ some of you have missed to do anything well.A. whatB. whichC. thatD. when10. _______ we are doing has never been done before.A. ThatB. WhatC. WhichD. Whether2）家庭作业：1. _____ as much as one-fifth of all timber harvested is not used.A. The estimateB. The estimatedC. They are estimatedD. It is estimated that2. _____ some mammals came to live in the sea is not known.A. WhichB. SinceC. AlthoughD. How3. _____ we have achieved is attributed to the guidance of our parents.A. WhoeverB. WhateverC. HoweverD. That4. _____ wealthy does not necessarily mean that a man is greedy.A. For the reason that he isB. Just because he isC. The reason of beingD. That he is5. Although ___ happened in this developed country sounds like science fiction, it c ould occurelsewhere in the world.A. whichB. whatC. howD. it6. _____ she had forgotten to take her notebook.A. That occurred to herB. She occurred thatC. To her that occurredD. It occurred to her that7. I am sure that _____ she said is wrong.A. whichB. allC. thisD. what8. We lost our way in the forest, and ____ made matters worse was that it was getting dark.A. thatB. whichC. itD. what9. _____ or not is still uncertain.A. He’s comingB. If he is comingC. That comingD. Whether he’s coming10. It’s _____ he’ll be able to come.A. doubt whetherB. doubtfulC. doubt itD. doubtful whether11. ______ he is at work in the heart of the big city or at home in the quiet suburb, Di ck’s life is tied to machines.A. WhetherB. TillC. IfD. Unless12. _____ he saw both surprised and frightened him.A. ThatB. WhenC. WhatD. Which13. _____ is warm sunshine.A. What do we all need.B. What all we needC. What we needD. What we all need14. _____ is a pity that he should feel so upset.A. WhatB. ThatC. HeD. It15. _____ a spoonful of soil can tell us so much about the structure and early history of the moon.A. RemarkableB. Quite remarkablyC. It is remarkable thatD. It is remarkable fact that16. _____ you nominate will be elected.A. WhoB. WhomC. WhomeverD. That’s17. _____ book you borrow must be returned within a week.A. WhatB. WhichC. WhicheverD. That’s18. _____ of us gets home first starts cooking.A. WhoB. WhichC. WhicheverD. Anyone19. It’s known to us all ___ a form of energy .A. water isB. that water isC. is waterD. that water to20. It worried her a bit ___ her hair was turning gray.A. whetherB. thatC. whatD. when21.What I say and think ___ none of your business.A. isB. areC. has D have22.___ is known to us all that America is a developed country .A WhichB AsC WhatD It23. ___we’ll go camping tomorrow depends on the weather .A IfB WhetherC ThatD Where24.___ he made an important speech at the meeting was true.A. ThatB. WhyC. WhatD. How答案：1）1-5 ADCBC 6-10 BBDCB2)19-24 BBADBA。