高中英语语法精讲精练---名词性从句

高中英语名词性从句知识讲解以及练习题附答案一、名词性从句概述名词性从句是一种充当名词作用的从句，通常在主句中作主语、宾语、表语或同位语。

它通常由引导词（如that, whether, if, who, whom, whose, which, what等）引导，并且从句中含有一个主语和谓语。

名词性从句的种类有很多，包括主语从句、宾语从句、表语从句和同位语从句等。

下面我们将逐一介绍这些从句。

二、主语从句主语从句作为一个名词，通常位于句首，是一个句子，主要作用是作为主句的主语。

引导主语从句的词：What (什么)；Whether (是否)；If (是否)；That (那个)。

例句：What he said is true. (他说的是真的。

)Whether it will rain tomorrow is uncertain. (明天是否会下雨还不确定。

)If you go, I will go too. (如果你走，我也跟着走。

)That he is coming is good news. (他来的消息是好消息。

)注意：主语从句的谓语动词通常要用单数形式。

What引导的主语从句通常用来表示“事物”的概念。

三、宾语从句宾语从句是一个名词，通常位于主句的动词后面，作为主句的宾语。

它可以由常见的宾语从句引导词引导，例如whether, if, that, who, whom, whose, what, when, where, how等。

引导宾语从句的词：Whether (是否)；If (是否)；That (那个)；Who (谁)；Whom (谁)；Whose (谁的)；What (什么)；When (何时)；Where (何处)；How (如何)。

例句：I know that he is coming. (我知道他要来。

)I wonder if he is telling the truth. (我想知道他是否说了真话。

语法复习之名词性从句名词性从句相当于名词，可分别作主句的主语、表语、宾语和同位语。

因此，名词性从句厅分为主语从句、表语从句、宾语从句和同位从句。

（一）引导名词性从句的连接词1、连接代词：who, whose, whom, what, which。

有词义，在从句中担任成分，如主语、表语、宾语、或定语等。

2、连接副词：when, where, why, how。

有词义，在从句中担任成分，作状语。

3、连接词：that, whether, if, as if。

that 无词义，在从句中不担任成分，有时可省略；if (whether), as if虽有词义，但在从句中不担任成分。

注意：连接代词与连接副词在句中不再是疑问句，因而从句中谓语不用疑问式。

连接代词与连接副词在从句充当句子成分，连接词whether 和if（是否），as if（好象）在从句中不充当句子成分，只起连接作用。

根据句义，如果连接代词与连接副词，whether、if 和as if都用不上时，才用that作连接词（that本身无任何含义）。

（二）主语从句1、主语从句在复合句作主语。

e.g. Who will go is not important.2、用it作形式主语，主语从句放在句末。

e.g. It doesn’t matter so much whether you will come or not.3、that引导主语从句时，不能省略。

e.g. That he suddenly fell ill last week made us surprised.（三）表语从句1、表语从句在复合句中作表语，位于系动词之后。

e.g. The question was who could go there.2、引导表语从句的连接词that有时可省去。

e.g. My idea is (that) we can get more comrades to help in the work.（四）宾语从句1、宾语从句在复合句中作宾语。

语法专题二：名词性从句1. 名词性从句的基本概念：1) 主语从句：在句中充当主语；亦可用it作形式主语，主语从句置于句末。

2) 宾语从句：在句中充当及物动词或介词的宾语；亦可用it作形式宾语，宾语从句置于句末。

3) 表语从句：在句中充当系动词的表语。

4) 同位语从句：常置于fact, idea, news, promise, doubt, suggestion, possibility, belief等表示有内容的名词后，起解释、说明作用。

2. 注意：1) 名词性从句要用陈述句语序。

2) 名词性从句中缺少主语、表语、宾语时：常用what 导，亦可用which表示选择，用who/whom/whoever指人。

缺少状语：用where（表地点）, when（表时间）, how（表方式）, why（表原因）。

3) 如不缺成份：主语从句、同位语从句用that引导，不能省略；表从、单个动词宾从可省略引导词that；介词宾从、第二个宾从，引导词that一般不省略；it作形式主语或宾语时，引导实际主从或宾从，一般that不省略；当主从、宾从本身为复合句时，引导词that不省略。

如：He told us sadly that what he had done secretly was dis covered by his parents.4) 含宾从的复合句中，主句和从句的时态保持一致，但如果从句中表示是客观现象，虽然主句是过去时态，从句仍用一般现在时。

5) 主语从句做主语，谓语动词用单数；如果由and 连接两个或两个以上的主语从句做主语时，谓语动词用复数；由两个或多个连接词引导一个主语从句，谓语动词用单数。

6) 当主句是I/We think（或suppose, expect, believe, imagine, guess）时，其后的宾语从句如果是否定的，常常把否定词not从从句中移到主句中。

7) 只能用whether，不能用if表示“是否”的情况如下：(1) 在表语从句和同位语从句中；(2) 在主语从句中，如果用it做形式主语，whether和if都能引导主语从句，否则，只能用whether(3) 在介词之后；(4) 后面直接跟动词不定式；(5) 与or not连用；(6) 引导让步状语从句，只能用whether。

高考英语语法复习名词性从句讲解练习名词性从句是指在复合句中起名词作用的句子，功能相当于名词词组。

名词性从句在复合句中能作主语、宾语、表语、同位语等，根据在句中的语法功能可分为主语从句、宾语从句、表语从句和同位语从句。

一、主语从句【定义】在复合句中，作主语的句子称为主语从句。

【常见的连接词】（连接词在句中不能省略）that, whether, who, what, whatever, whoever, where, when, why, how等。

【用法】连接词 that 引导That we should learn English well is very important.主语从句中 we should learn English well句子完整，不缺成分，用that引导，that 不能省连接词whether，if 引导whether 引导的主语从句可放句首，也可放句中，表“是否”if 引导的主语从句只能引导动词后的宾语Whether I will go or not depend on the weather.It remains to be seen whether / if they can finish the task in time.2.连接代词what, who, which, whose, whatever, whichever，whoever等引导What matters most is your attitude.3.连接副词when，where，why，how等引导How he made it is still unknown.4.it作形式主语为了避免句子头重脚轻，通常把形式主语it放在句首，真正的主语放在句子后面。

常见句型：(1) It is + n.+ that + 句子It is +（a pity / a shame / a fact …）+ that ...(2) It is + adj.+ that + 句子It is +（true / clear / important …）+ that ...(3) It is + 过去分词 + that + 句子It is+ said / announced / expected / believed / hoped… + that ...(4) It seems /appears / happens / turned out that + 句子(5) It hit sb./occurred to sb.that + 句子二、宾语从句【定义】在复合句中，作宾语的句子称为宾语从句。

名词性从句讲解思维导图（附练习题）（在句子中作主语成分）③whatever /whichever/ whoever引导主语从句的区别ⅠWhatever 是what的强调形式表示“无论什么”相当于anything that…Whatever / Anything that she does is wrong.Ⅱwhoever 是who的强调形式，表示‘无论谁’ 相当于anyone who….Whoever / Anyone who walks around in such a heavy rain willcatch a cold.whichever ‘无论哪个;无论哪些’,既指人,又指物. 可修饰名词与of连用Whichever book you borrow doesn’t matter to us.Whichever of us fulfills his task will lend a hand to others.定义：在复合句中充当宾语功能的句子叫宾语从句We can learn what we didn’t know.We find it necessary that we (should) practice English every day.★某些作表语的形容词，如sure, happy, glad, certain等之后可带宾语从句I am glad that you can come and help me.wish/would rather后的宾语从句中要用虚拟语气。

I wish I had finished my homework yesterday.I’d rather you had been there yesterday②在表示建议,命令, 请求的词后面的宾语从句当中用should + V,可以省略His pale face suggested that he was ill so I suggested that he should goto see the doctor.He insisted that he was innocent and insisted that he should be set free.③注意it作形式宾语的结构We all thought it a pity that we had missed the lesson.I took it for granted that they were not coming.④ that一般不接介词宾语，偶尔可作except, in的宾语；其它介词后面需用it作形式宾语He differs from his roommates in that he devoted his spare time toreading.He knows nothing about Jim except that he is from London.You can depend on it that he will help you in time of emergency.定义：充当表语功能的句子被叫做表语从句。

名词性从句精讲来源：普特英语在复合句中起名词作用的从句叫名词性从句，包括作主语从句、表语从句、宾语从句和同位语从句。

(1)主语从句就是在复合句中作主语的从句。

主语从句常用that, whether, who, whom, whose, what, which, when, where, how, why, whatever, whoever等引导。

如：Whether he will be able to come remains a question. 他是否来还是问题。

That China is a great socialist country is well known. 众所周知，中国是一个伟大的社会主义国家。

注：为避免头重脚轻，使句子平衡，常用it作形式主语，而将主语从句后置。

如上述第二例常说成：It is well known that China is a great socialist country.但是，由连接代词what, whatever, whoever等引导的主语从句一般不能用形式主语。

如：What he found surprised me greatly. 他的发现使我非常吃惊。

Whoever is finished may rest. 凡是做完工的人都可以休息。

(2)表语从句就是在连系动词之后作表语的从句。

引导表语从句的连接除与引导主语从句的连接词外，还有as if，as though。

如：The question is whether he is able to do it alone. 问题是他能否单独做这件事。

It looks as if (though) it is going to snow. 天好像要下雪似的。

注意：要区分以下句式：1. that’s why+结果；that’s because+原因。

2. the reason why /for…is that…He is absent. That’s because he is ill. 他缺席，这是因为他生病了。

名词性从句一、知识储备二、考点及考查频率1．宾语从句：①连接代词 (32/101 )②连接副词(11/101 ) ③连接词(2/101)2. 主语从句：①连接代词(14/101) ②连接词(1/101)3. 表语从句：①连接副词(6/101) ②连接代词 (3/101)4. 同位语从句：(16/101)5.wh-ever引导的名词性从句：(10/101)6.that用法(6/101)（1）宾语从句连接代词高三1.How much one enjoys himself travelling depends largely on he goes with，whether his friends or relatives．A．what B．who C．how D．why2. I want to be liked and loved for I am inside.名词性从句A. whoB. whereC. whatD. how3.Before the sales start, I make a list of ______ my kids will need for the coming season.名词性从句A. whyB. whatC.howD. which4. As a new graduate, he doesn’t know it takes to start a business here.A. howB. whatC. WhenD. which5. Many young people in the West are expected to leave __ could be life' s most important decision -- marriage -- almost entirely up to luck.A. asB. thatC. whichD. what6.2.The companies are working together to create _____ they hope will be the best means of transport in the 21st century.A. whichB. thatC. whatD. who7.When asked _____ they needed most, the kids said they wanted to feel important and loved.A. whatB. whyC. whomD. which8.People in Chongqing are proud of they have achieved in the past ten years.A. thatB. whichC. whatD. how9.Some children want to challenge themselves by learning a language different from ____ their parents speak at home.A. whatB. thatC. whichD. one10.You can only be sure of ____you have at present; you cannot be sure of something ___ you might get in the future.A. that; whatB. what; /C. which; thatD. /; that11.Choosing the right dictionary depends on ______you want to use it for.A. whatB. whyC. howD. whether12.By improving reading skills, you can read faster and understand more of you read．A．that B．what C．which D．whether13.--- Could you do me a favour?--- It depends on ______ it is.A. whichB. whicheverC. whatD. whatever14.–What did your parents think about your decision?–They always let me do _____ I think I should.A. whenB. thatC. howD. what15.He spoke proudly of his part in the game, without mentioning ____ his teammates had done.A. whatB. whichC. whyD. while16.I was surprised by her words, which made me recognize ___ silly mistakes I had made.A. whatB. thatC. howD. which17.The way he did it was different _______ we were used to .A．in which B．in what C．from what D．from which18.The shopkeeper did not want to sell for ______ he thought was not enough.A. whereB. howC. whatD. which19.The other day, my brother drove his car down the street at ___ I thought was a dangerous speed.A. asB. whichC. whatD. that20.A modern city has been set up in ＿＿＿was a wasteland ten years ago .A. whatB. whichC. thatD. where21.I think Father would like to know ____ I've been up to so far, so I decide to send him a quick note.A. whichB. whyC. whatD. how22.After Yang Li wei succeeded in circling the earth, _______ our astronauts desireto do is walk in space.A. whereB. whatC. thatD. how23.People have heard what the President has said；they are waiting to see _____ hewill do．A．how B．what C．when D．that24.—I think it’s going to be a big problem. —Yes, it could be.—I wonder ＿＿ we can do about it.A. ifB. howC. whatD. that25.When you answer questions in a job interview. Please remember the golden rule;Always give the monkey exactly ＿＿ he wants.A. whatB. whichC. whenD. that26.The mother didn't know _____ to blame for the broken glass as it happened whileshe was out.A. whoB. whenC. howD. what27.It is said in Australia there is more land than the government knows ____.A. it what to do withB. what to do it withC. what to do with itD. to do whatwith it28.Perseverance is a kind of quality--- and that's ____ it takes to do anything well.A. whatB. thatC. whichD. why29.A computer can only do ____ you have instructed it to do.A. howB. afterC. whatD. when30.Little Tommy was reluctant to tell the schoolmaster ____ he had done the day before.A．That B．how C．Where D．what高二31.No one can be sure _____ in a million years.A.what man will look likeB. what will man look likeC. man will look like whatD. what look will man like高一32.These photographs will show you ______.A. what does our village look likeB. what our village looks likeC. how does our village look likeD. how our village looks like连接副词高三1.We haven’t dicussed yet _______ we are going to place our new furniture.名词性从句A．that B．which C．what D．where2.Cindy shut the door heavily and burst into tears. No one in the office knew shewas so angry.名词性从句A. whereB. whetherC. thatD. why3. —It’s no use having ideas only.—Don’t wo rry. Peter can show you to turn an idea into an act.名词性从句A. howB. whoC. whatD. where4.— I wonder ________ you’ll water this kind of flower .—Every other day.A. how oftenB. how longC. how soonD. how much5.Mary wrote an article on _______the team had failed to win the game .A．why B．what C．who D．that6.The old lady’s hand shook frequently. She explained to her doctor ______ this shaking had begun half a year before, and _____, only because of this, she had been forced to give up her job.A. when ; howB. how ; whenC. how ; howD. why ; why7.Parents are taught to understand ______ important education is to their children's future.A. thatB. howC. suchD. so高二8.—Do you remember ______ he came?—Yes, I do, he came by car.A. howB. whenC. thatD. if9.I remember____ this used to be a quiet village.A. whenB. howC. whereD. what10.Can you make sure ______ the gold ring?A.where Alice had putB.where had Alice putC.where Alice has putD.where has Alice put高一11.Can you tell me _____the railway station?A. how I can get toB. how can I get toC. where I can get toD. where canI get to连接词高三1.We haven't settled the question of ______ it is necessary for him to study abroad.A. ifB. whereC. whetherD. that高一2.Ask her_____ come with me.A if she willB if will sheC whether will sheD will she（2）主语从句连接代词高三1._____ is known to us all is that the 2008 Olympic Games will take place in Beijing.A. ItB. WhatC.As D. Which2._____ was most important to her, she told me, was her family.A. ItB. ThisC. WhatD. As3._____ matters most in learning English is enough practice.A. WhatB. WhyC. WhereD. Which4.It is none of your business ______ other people think about you. Believe yourself.It句型A. howB. whatC. whichD. when5. parents say and do has a life-long effect on their children.A. ThatB. WhichC. WhatD. As6.____ he referred to in his article was unknown to the general reader.A. ThatB. WhatC. WhetherD. Where7.____makes this shop different is that it offers more personal services.A. WhatB. WhoC. WhateverD. Whoever8.After Yang Li wei succeeded in circling the earth, _______ our astronauts desireto do is walk in space.A. whereB. whatC. thatD. how9.____ made the school proud was _____ more than 90%of the students had beenadmitted to key universities.A. What; becauseB. What; thatC. That; whatD. That; because10.It is pretty well understood ___ controls the flow of carbon dioxide in andout the atmosphere today. It句型A. thatB. whenC. whatD. how11.I read a bout it in some book or other, does it matter_______it was?A．where B．what C．how D．which高二12.____ he said at the meeting astonished everybody present.A. WhatB. ThatC. The factD. The matter高一13._______ you have done might do harm to other people.A. ThatB. WhatC. WhichD. This14.______ he said is true.A. WhatB. ThatC. WhichD. Whether连接词高二1____ the 2000 Olympic Games will be held in Beijing is not known yet.A. WheneverB. IfC. WhetherD. That（3）表语从句连接副词高三1.-I prefer shutting myself in and listening to music all day on Sundays.-Th at’s_______I don’t agree .You should have a more active life.A.whereB.howC.whenD.what2.The last time we had great fun was _____ we were visiting the Water Park.A. whereB. howC. whenD. why3.Why not try your lick downtown, Bob? That’s ______ the best jobs are.A. whereB. whatC. whenD. why4.You are saying that everyone should be equal, and this is _______I disagree.A. whyB. whereC. whatD. how高二5.－Idrove to Zhuhai for the air show last week. －Is that ＿＿ you had a few days off?A. whyB. whenC. whatD. where6.Go and get your coat. It's _____ you left it.A. thereB. whereC. there whereD. where there连接代词1.See the flags on top of the building? That was______ we did this morning. 连接A. whenB. whichC. whereD. What2.Great changes have taken place in that school. It is no longer _____ it was 20 years ago, _____ poorly equipped. 连接A. what; whenB. that; whichC. what; whichD. which; that3.—Are you still thinking about yesterday's game？—Oh，that's_____ ．A．what makes me feel excited B．whatever I feel excited aboutC．how I feel about it D．when I feel excited（4）同位语从句高三1.A warm thought suddenly came to me ______I might use the pocket money to buysome flowers for my mother’s birthday．A．if B．when C．that D．which2.--- It's thirty years since we lest met.--- But I still remember the story, believe it or not, ____we got lost on a rainy night.A. whichB. thatC. whatD. when3.There is much chance _____Bill will recover from his injury in time for therace.A. thatB. whichC. untilD. if4.Nobody believed his reason for being absent form the class ____he had to meethis uncle at the air port.A. whyB. thatC. whereD. because5.Along with the letter was his promise ____ he would visit me this comingChristmas.A. whichB. thatC. whatD. whether6.A story goes ______ Elizabeth I of England liked nothing more that beingsurrounded by clever and qualified noblemen at court.A. whenB. whereC. whatD. that7.There is a new problem involved in the popularity of private cars ____ roadconditions need ___.A. that; to be improvedB. which; to be improvedC. where; improvingD. when; improving8.There's a feeling in me ____ we'll never know what a UFO is ---not ever. (2002上海)A. thatB. whichC. of whichD. whatrmation has been put forward ___ more middle school graduates will beadmitted into universities.A. whileB. thatC. whenD. as10.News came from the school office ________Wang Lin had been admitted to Beijing University. A. which B. what C. that D. where 11. — Is there any possibility ________ you could pick me up at the airport ?— No problemA. whenB. thatC. whetherD. what12. We should consider the students’ request ___the school library provide more books on popular science.A. thatB. whenC. whichD. where13. The fact has worried many scientists ____ the earth is becoming warmer and warmer these years.A. whatB. whichC. thatD. though14.Tomorrow is Tom’s birthday. Have you got any idea the party is to be held?A. whatB. whichC. thatD. where15.Do you have any idea ________ is actually going on in the classroom?A．that B．what C．as D．which高一16.They have no idea at all ______ .A. where he has goneB. where did he goC. which place has he goneD. where has he gone（5）wh-ever引导的名词性从句高三1.-- How about camping this weekend, just for a change?-- OK, __ you want.（2010浙江）A. whicheverB. howeverC. whateverD. whoever2.______wants to stay in a hotel has to pay their own way.A. AnyoneB. The oneC. WhoeverD. Who3.____ team wins on Saturday will go through to the national championships.A. No matter whatB. No matter which C Whatever D. whichever4.The poor young man is ready to accept ______ help he can get.A．whichever B．however C．whatever D．whenever5.Eat _______ cake you like and leave the others for _______ comes in late.A. any; whoB. every; whoeverC. whichever; whoeverD. either; whoever6.These wild flowers are so special I would do ______ I can to save them.A. whateverB. thatC. whichD. whichever高二7.It is generally considered unwise to give a child _____he or she wants.A. howeverB. whateverC. whicheverD. whenever8. She is very dear to us. We have been prepared to do ______ it takes to save her life.A. whicheverB. howeverC. whateverD. whoever9.Could I speak to ______ is in charge of International Sales please?A. whoB. whatC. whoeverD. whatever10．The how-to book can be of help to _______ wants to do the job.A．who B．whomever C．no matter who D．whoever（6）that 用法高三1.Having checked the doors were closed , and ______ all the lights were off, the boy opened the door to his bedroom.A. whyB. thatC. whenD. where2.The thought of going back home was kept him happy while he was working abroad．A．that B．all that C．all what D．which3.The traditional view is ______ we sleep because our brain is “programmed” to make us do so.A. whenB. whyC. whetherD. that4.With his work completed, the businessman stepped back to his seat, feeling pleased ____he was a man of action.A. whichB. that C .what D. whether5.____ made the school proud was _____ more than 90%of the students had been admitted to key universities.A. What; becauseB. What; thatC. That; whatD. That; because6.＿＿ fashion differs from country to country may reflect the cultural differences from one aspect.A. WhatB. ThatC. ThisD. Which三、易错题1.I prefer shutting myself in and listening to music all day on Sundays.-That’s_______I don’t agree .You should have a more activ e life.A.whereB.howC.whenD.what2. I want to be liked and loved for I am inside.名词性从句A. whoB. whereC. whatD. how3.The last time we had great fun was _____ we were visiting the Water Park.A. whereB. howC. whenD. why4.______wants to stay in a hotel has to pay their own way.A. AnyoneB. The oneC. WhoeverD. Who5.You can only be sure of ____you have at present; you cannot be sure of something ___ you might get in the future.A. that; whatB. what; /C. which; thatD. /; that6.Having checked the doors were closed , and ______ all the lights were off, the boy opened the door to his bedroom.A. whyB. thatC. whenD. where7.Why not try your lick downtown, Bob? That’s ______ the best jobs are.A. whereB. whatC. whenD. why8.The thought of going back home was kept him happy while he was working abroad．A．that B．all that C．all what D．which9.The traditional view is ______ we sleep because our brain is “programmed” to make us do so.A. whenB. whyC. whetherD. that10.____ team wins on Saturday will go through to the national championships.A. No matter whatB. No matter which C Whatever D. whichever11.Great changes have taken place in that school. It is no longer _____ it was 20 years ago, _____ poorly equipped.A. what; whenB. that; whichC. what; whichD. which; that12.Some researchers believe that there is no doubt ______ a cure for AIDS will be found.A. whichB. thatC. whatD. whether13.The old lady's hand shook frequently. She explained to her doctor ______ this shaking had begun half a year before, and _____, only because of this, she had been forced to give up her job.A. when; howB. how; whenC. how; howD. why; why14.Parents are taught to understand ______ important education is to their children's future.A. thatB. howC. suchD. so15.You are saying that everyone should be equal, and this is _______I disagree.A. whyB. whereC. whatD. how16.＿＿ fashion differs from country to country may reflect the cultural differences from one aspect.A. WhatB. ThatC. ThisD. Which17.____ the 2000 Olympic Games will be held in Beijing is not known yet.A. WheneverB. IfC. WhetherD. That18.No one can be sure _____ in a million years.A.what man will look likeB. what will man look likeC. man will look like whatD. what look will man like19.We should consider the students’ request ___the school library provide more books on popular science. (重庆)A. thatB. whenC. whichD. where答案1、宾语从句ACBB D CACAB ABCDA ACCCA CBBCA ACACD A BDDA AA CBACA2、主语从句BCABC BABBC BABAC3、表语从句A CABA BDAA4、同位语从句CBABB DAABC BACCA A5、wh-ever引导的名词性从句C CDCC ABCCD6、that用法BBDBB B易错题AC CCB BABDD ABCBB BCAA。

高中英语名词性从句详细讲解与练习在句子中起名词作用的从句叫名词性从句。

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，因此根据它在句中不同的语法功能，名词性从句又可分为主语从句、宾语从句、表语从句、同位语从句。

引导名词性从句的词叫做连接词，包括：1.连词（在名词性从句中只起连接作用，不作成分）2.连接代词（在名词性从句中作主语、宾语或表语）3.连接副词（在名词性从句中作状语）所有的名词性从句的语序都是陈述语序。

I主语从句：是在主句中作主语的从句。

它由连接词引导，通常位于谓语动词之前。

连接词：1.连词：在从句中不充当任何成分，常见的引导主语从句的连词有that, whether oThat he got the first prize excited him much.他获得一等奖一事使他非常兴奋。

It is doubtful whether we can get there on time.我们能否按时到达那儿还不确定。

D that引导的主语从句:在从句中不作任何成分，也没有实际意义。

一般情况下that不可省略。

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.你不喜欢他不关我的事。

2）whether引导的土语从句:常置于句首，表示“是否”之意；if一般不引导主语从句。

Whether he can finish his task on time is of greatimportance.他是否能按时完成任务非常重要。

Whether you can succeed or not depends on howhard you work at it.你能否成功取决于你努力的程度。

2.连接代词：在从句中起名词或代词的作用，常作从句的主语、宾语、表语或定语,有具体意义且不能省略。