英語從句大全

1、英語從句大全1）表語從句1.定義：用作表語的從句叫做表語從句。2.構(gòu)成：關(guān)聯(lián)詞+簡單句3.引導(dǎo)表語從句的關(guān)聯(lián)詞的種類：（1）從屬連詞that.如：The trouble is that I have lost his address.麻煩是我把他的地址丟了。（2）從屬連詞whether，as，as if.如：He looked just as he had looked ten years before.他看起來還與十年前一樣。The question is whether they will be able to help us.問題是他們是否能幫我們。注：從屬連詞if一般不用來引導(dǎo)表語從句

2、，但as if卻可引導(dǎo)表語從句，如：All this was over twenty years ago，but its as if it was only yesterday.這都是20多年前的事了，但宛如昨天一樣。能跟表語從句的謂語動詞一般為系動詞be，seem，look等。如：It looked as if it was going to rain.看起來天要下雨了。（3）連接代詞who，whom，whose，what，which，whoever，whatever，whichever連接副詞 where，when，how，why.如：The problem is who we can g

3、et to replace her.問題是我們能找到誰去替換她呢。The question is how he did it.問題是他是如何做此事的。That was what she did this morning on reaching the attic.那就是她今晨上了閣樓干的。解釋：1.連詞because可引導(dǎo)表語從句。如：I think it is because you are doing too much.我想這是因為你做得太多。2.在一些表示“建議、勸說、命令”的名詞后面的表語從句中，謂語動詞用虛擬語氣。should+動詞原形表示，should可省略。如：My sugges

4、tion is that we （should）start early tomorrow.我的建議是我們明天一早就出發(fā)。2）主語從句1.定義：用作主語的從句叫做主語從句。2.構(gòu)成：關(guān)聯(lián)詞+簡單句3.引導(dǎo)主語從句的關(guān)聯(lián)詞有三類：（1）從屬連詞that.如：That they were in truth sisters was clear from the facial resemblance between them.很明顯，她們確是親姐妹，她們的臉型很相似。（2）從屬連詞whether.如：Whether hell come here isnt clear.他是否會來這里還不清楚。（3）連接代

5、詞who，whom，whose，what，which，whoever，whatever，whichever連接副詞 where，when，how，why.如：What she did is not yet known.她干了什么尚不清楚。How this happened is not clear to anyone.這事怎樣發(fā)生的，誰也不清楚。Whoever comes is welcome.不論誰來都?xì)g迎。Wherever you are is my home my only home.你所在的任何地方就是我的家我唯一的家。解釋：1.主語從句能用it作形式上的主語。常以it作形式主語的句型

6、有：A.It+be+形容詞（obvious，true，natural，surprising，good，wonderful，funny，possible，likely，certain，probable，etc.）+that從句。如：It is certain that she will do well in her exam.毫無疑問她考試成績會很好。It is probable that he told her everything.很可能他把一切都告訴她了。B.It+be+名詞詞組（no wonder，an honor，a good thing，a pity，no surprise，etc.

7、）+that從句。如：Its a pity that we cant go.很遺憾我們不能去。Its no surprise that our team should have won the game.我們沒贏這場比賽真意外。C.It+be+過去分詞（said，reported，thought，expected，decided，announced，arranged，etc.）+that從句。如：It is said that Mr. Green has arrived in Beijing.據(jù)說格林先生已經(jīng)到了北京。It is reported that China has sent ano

8、ther man-made earth satellite into orbit.據(jù)報道中國又成功地發(fā)射了一顆人造地球衛(wèi)星。D.It+seem，happen等不及物動詞及短語+that從句。如：It seems that Alice is not coming to the party at all. Alice似乎不來參加晚會。It happened that I was out that day.碰巧我那天外出了。E.It+doesnt matter（makes no difference，etc.）+連接代詞或連接副詞引起的主語從句。如：It doesnt matter whether

9、she will come or not.她是否來這無關(guān)緊要。It makes no difference where we shall have the meeting.我們在哪里開會毫無區(qū)別。F.當(dāng)that引導(dǎo)的主語從句出現(xiàn)在疑問句中時，要以it作形式主語，而把主語從句后置。如：Is it true that the scientist will give us a lecture next week？ 下周那位科學(xué)家將給我們作報告是真的嗎？Does it matter much that they will not come tomorrow？ 他們明天不來很要緊嗎？G.當(dāng)主語從句出現(xiàn)在

10、感嘆句中時，要以it作形式主語，而把主語從句后置。如：How strange it is that the children are so quiet！ 孩子們這么安靜真奇怪！2.注意連接代詞whoever，whatever，whichever等引導(dǎo)主語從句的含義。Whoever comes will be welcome.（whoever=the person who）來的人將受到歡迎。Whatever he did was right.（whatever=the thing that）他所做的事情是正確的。Whichever of you comes in will receive a p

11、rize.（whichever=anyone of you who）你們當(dāng)中不論哪個進(jìn)來將會得到獎3）賓語從句1.定義：用作賓語的從句叫賓語從句。2.構(gòu)成：關(guān)聯(lián)詞+簡單句。3.引導(dǎo)賓語從句的關(guān)聯(lián)詞有三類：（1）從屬連詞that.如：He told us that he felt ill.他對我們說他感到不舒服。I know he has returned.我知道他已經(jīng)回來了。注： that在引導(dǎo)賓語從句時也并不是任何情況下都可以省略。在以下情況下，that不能省略。1. Everybody could see what happened and that Tom was frightened.

12、（and連接兩個賓語從句，that賓語從句放在and的后面時，that不能省略。）大家都會看出所發(fā)生的事情并知道Tom非常害怕。2. I know nothing about him except that he is from the south.（that引導(dǎo)的賓語從句作介詞賓語時，that不能省略。）對他我一無所知，只知道他是南方人。3. That he ever said such a thing I simply dont believe.（that從句位于句首時，that不可省略。）我簡直不相信他曾說過這樣的話。4.We decided，in view of his special

13、 circumstances，that we would admit him for a probationary period.（主句謂語動詞與that從句之間有插入語，that不可省略。）鑒于他的特殊情況，我們決定應(yīng)允他一段試用期。（2）從屬連詞if/whether.如：I doubt whether he will succeed.我懷疑他是否會成功。I dont know if you can help me.我不知道你能否幫助我。（3）連接代詞who，whom，whose，what，which，whoever，whatever，whichever連接副詞 where，when，how

14、，why. 如：Who or what he was，Martin never learned.他是什么人？他是干什么的？馬丁根本不知道。I wonder what hes writing to me about.我不知道他要給我寫信說什么事。Ill tell you why I asked you to come.我會告訴你我為什么要你來。You may do what you will.你可做任何你想做的事。類型：（1）介詞賓語從句賓語從句也可用作介詞的賓語。如：He was deeply displeased by what had occurred that day.他對那天發(fā)生的事感

15、到很不快。I walked over to where she sat.我走向她坐的地方。I am curious as to what he will say.我很想知道他要說什么。Your success will largely depend upon what you do and how you do it.你是否成功將主要取決于你做什么和怎樣做。有時介詞可以省略。如：I dont care （for）who marries him.我不管誰跟他結(jié)婚。Be careful （as to）how you do that.你要注意做這件事的方式。解釋：1.如果賓語從句后還有賓語補足語，則

16、用it作形式賓語，而將賓語從句后置。如：We thought it strange that Xiao Wang did not come yesterday.我們認(rèn)為小王昨天沒來是奇怪的。He has made it clear that he will not give in.他已表明他不會屈服。2.作介詞的賓語：連詞that引導(dǎo)的名詞性從句很少作介詞的賓語，只用在except，but，in后。其他一些介詞的賓語從句如果由連詞that引導(dǎo)，則需用it先行一步，作形式賓語。如：He is a good student except that he is careless.他是一個好學(xué)生，只是

17、有點粗心。You may rely on it that I shall help you.你可以指望我會幫助你的。介詞賓語不可以用which來引導(dǎo)，而要用what來引導(dǎo)。如：Are you sorry for what youve done？你為你所做的一切感到內(nèi)疚嗎？3.某些形容詞或過去分詞后常接賓語從句，這類形容詞或過去分詞有sure，glad，certain，pleased，happy，afraid，surprised，satisfied等，連詞that可省略。如：I am not sure what I ought to do.我不能確定我該做什么。Im afraid you don

18、t understand what I said.恐怕你沒領(lǐng)會我說的意思。Im surprised that I didnt see all that before.我好奇怪，我以前沒看到過。Mother was very pleased her daughter had passed the exams.媽媽為她的女兒通過了考試而感到高興。4.連詞whether （or not）或if引導(dǎo)的賓語從句if和whether引導(dǎo)的賓語從句可以互換使用，但whether常和or not連用，if一般不與or not連用。如：I wonder whether it is true or not.我不知

19、它是真是假。用if引導(dǎo)賓語從句如果會引起歧義，應(yīng)避免使用if而用whether.試比較：Please let me know if you want to go.Please let me know whether you want to go.if從句可理解為賓語從句，意為“請告訴我你是否想去”；此句又可理解為條件狀語從句意為“如果你想去的話，請告訴我一聲”。5.賓語從句的否定轉(zhuǎn)移。在think，believe，suppose，expect等動詞后的賓語從句，有時謂語盡管是否定意思，卻不用否定形式，而將think等動詞變?yōu)榉穸ㄐ问?。如：I dont think you are right.我

20、認(rèn)為你錯了。I dont believe they have finished their work yet.我相信他們還未完成他們的工作。I dont suppose he cares，does he？ 我想他不在意，是嗎？6.賓語從句的時態(tài)變化規(guī)律：（1）當(dāng)主句是一般現(xiàn)在時態(tài)時，從句可根據(jù)需要用任何時態(tài)。（2）當(dāng)主句是一般過去時態(tài)時，從句只能使用過去范圍內(nèi)的任何時態(tài)。但客觀真理除外。如：The teacher said that the earth goes round the sun.老師說地球繞著太陽運行。4）同位語從句1.定義：用作同位語的從句叫做同位語從句。2.用法：同位語從句的先

21、行詞多為fact，news，idea，thought，question，reply，report，remark等，關(guān)聯(lián)詞多用從屬連詞that.如：They were all very much worried over the fact that you were sick.對你生病這件事，他們都很焦慮。Where did you get the idea that I could not come？你在哪兒聽說我不能來？Early in the day came the news that Germany had declared war on Russia.德國已對俄國宣戰(zhàn)的消息一大早就傳

22、來了。注：同位語從句偶爾由從屬連詞whether引導(dǎo)。如：I have no idea whether hell come or not.我不知道他是否來。連接代詞who，which，what和連接副詞where，when，why，how亦可引導(dǎo)同位語從句。The question that should do the work requires consideration.誰該干這項工作，這個問題需要考慮。We havent yet settled the question where we are going to spend our summer vacation.到哪兒去度暑假，這個問

23、題我們還沒有決定。It is a question how he did it.那是一個他如何做了此事的問題。解釋：1.that引導(dǎo)的同位語從句與定語從句之區(qū)別that引導(dǎo)的同位語從句that引導(dǎo)的定語從句句法功能上that只起連接從句的作用，無意義。在從句中不充當(dāng)句子成分。不可省。that替代先行詞在從句中不僅起連接作用，還充當(dāng)一個句子成分。如在從句中作動詞的賓語時可省略。意義上從句是被修飾名詞的內(nèi)容。從句起限定作用，是定語如：The news that Mr.Li will be our new English teacher is true.（同位語從句，that不可省。）李先生將是我們

24、的新英語老師這個消息是真的。The news （that）he told me yesterday is true.（定語從句，that在從句中作told的賓語，可省。）他昨天告訴我的消息是真的。2.一些表示“建議、命令、要求”的名詞后所跟的同位語從句中，謂語動詞用虛擬語氣should+動詞原形表示。should可省。如：This is our only request that this （should）be settled as soon as possible.這就是我們唯一的請求：盡快解決這個問題。5）定語從句定語從句及相關(guān)術(shù)語 1.定語從句：定語從句是由關(guān)系代詞或關(guān)系副詞引導(dǎo)的從句，

25、其作用是作定語修飾主句的某個名詞性成分，相當(dāng)于形容詞，所以又稱為形容詞性從句，一般緊跟在它所修飾的先行詞后面。2.關(guān)系詞：引導(dǎo)定語從句的關(guān)聯(lián)詞稱為關(guān)系詞，關(guān)系詞有關(guān)系代詞和關(guān)系副詞。關(guān)系代詞有that, which, who, whom, whose, as等；關(guān)系副詞有where, when, why等。關(guān)系詞常有3個作用：1，引導(dǎo)定語從句。2，代替先行詞。3，在定語從句中擔(dān)當(dāng)一個成分。注：關(guān)系代詞有主語.賓語之分。一般whom作為賓語。4.定語：定語用來限定、修飾名詞或代詞的，是對名詞或代詞起修飾、限定作用的詞、短語或句子，漢語中常用的表示。主要由形容詞擔(dān)任。此外，名詞，代詞，數(shù)詞，分詞，

26、副詞，不定式以及介詞短語也可以來擔(dān)任，也可以由一個句子來擔(dān)任單詞作定語時通常放在它所修飾的詞之前，作前置定語。短語和從句作定語時則放在所修飾的詞之后，作后置定語。限定性定語從句一、關(guān)系代詞（在句中作主語、賓語或定語）1. that既可代表事物也可代表人，which代表事物；它們在從句中作主語或賓語，that在從句中作賓語時常可省略關(guān)系詞，which在從句中作賓語也可以省略。eg：this is the book （which）you want。而且，如果which在從句中作“不及物動詞介詞”的介詞的賓語，注意介詞不要丟掉，而且介詞總是放在關(guān)系代詞which的前邊，但有的則放在它原來的位置 2.

27、 which作賓語時，根據(jù)先行詞與定語從句之間的語義關(guān)系，先行詞與which之間的介詞不能丟3. 代表物時多用which，但在帶有下列詞的句子中用that而不用which，這些詞包括當(dāng)先行詞是anything, everything, nothing , none等不定代詞時，或者是由every, any, all, some, no, little, few, much等修飾時等，這時的that常被省略 還有先行詞前有序數(shù)詞或形容詞最高級修飾時,或先行詞就是序數(shù)詞或最高級時.以及先行詞中既有人又有物時.還有句中前面有which時,都只能用that4. who和whom引導(dǎo)的從句用來修飾人，分

28、別作從句中的主語和賓語，whom作賓語時，要注意它可以作動詞的賓語也可以作介詞的賓語 5. whose是關(guān)系代詞，修飾名詞作定語，相當(dāng)于所修飾成分的前置所有格.它引導(dǎo)的從句可以修飾人和物, 當(dāng)它引導(dǎo)的從句修飾物體時, 可以與 of which 調(diào)換,表達(dá)的意思一樣。二、關(guān)系副詞（在句中作狀語）關(guān)系副詞=介詞+關(guān)系代詞Why=for whichWhere=in/ at/ on/ . which (介詞同先行詞搭配)When=during/ on/ in/ . which (介詞同先行詞搭配)1. where是關(guān)系副詞，用來表示地點的定語從句。2. when引導(dǎo)定語從句表示時間注值得一提的是，表示

29、時間“time"一詞的定語從句只用when引導(dǎo)，有時不用任何關(guān)系代詞，當(dāng)然也不用that引導(dǎo)。 By the time you arrive in London, we will have stayed there for two weeks. I still remember the first time I met her. Each time he goes to business trip, he brings a lot of living necessities, such as towels, soap, toothbrush etc。3. 當(dāng)從句的邏輯主語是some,

30、 any, no, somebody, anybody, nobody, something, anything, everything或nothing時，常用there is來引導(dǎo)There is somebody here who wants to speak to you. 這里有人要和你說話。非限定性定語從句非限定性定語從句的作用是對所修飾的成分作進(jìn)一步說明，通常是引導(dǎo)詞和先行詞之間用逗號隔開，將從句拿掉后其他部分仍可成立 1. which引導(dǎo)的非限定性定語從句來說明前面整個句子的情況或主句的某一部分 2.當(dāng)先行詞是專有名詞或物主代詞和指示代詞所修飾時，其后的定語從句通常是非限制性的，

31、例如：Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了，他曾經(jīng)是我的老師。My house, which I bought last year, has got a lovely garden.我去年買的的那幢房子帶著個漂亮的花園。 This novel, which I have read three times, is very touching. 這本小說很動人，我已經(jīng)讀了三遍。3.非限制性定語從句還能將整個主句作為先行詞, 對其進(jìn)行修飾, 這時從句謂語動詞要用第三人稱單數(shù)，例如：H

32、e seems not to have grasped what I meant, which greatly upsets me. 他似乎沒抓住我的意思，這使我心煩。Liquid water changes to vapor, which is called evaporation. 液態(tài)水變?yōu)檎羝@就叫做蒸發(fā)。4. 有時as也可用作關(guān)系代詞5. 在非限定性定語從句中，不能用關(guān)系副詞why和關(guān)系代詞that，而用who, whom代表人，用which, whose代表事物.；關(guān)系代詞引導(dǎo)的定語從句1.who指人在從句中做主語(1) The boys who are playing foot

33、ball are from Class One.(2) Yesterday I helped an old man who lost his way.2. whom指人，在定語從句中充當(dāng)賓語，?？墒÷浴＃ㄗⅲ簑ho和whom已無太大區(qū)別，可以通用。）(1) Mr. Liu is the person (whom) you talked about on the bus.(2) Mr. Ling is just the boy whom I want to see.(3) The man who/whom you met just now is my friend.注意：關(guān)系代詞whom在口語和

34、非正式語體中常用who代替，可省略。如果在從句中做賓語,就用whom或who.比如: He is the man whom/who I talk to. 如果是在從句中作主語就只能用who.比如: He is the man who has an English book.3.which指物，在定語從句中做主語或賓語，做賓語時可省略(1) Football is a game which is liked by most boys.(2) This is the pen (which) he bought yesterday. 4. that指人時，相當(dāng)于who或者whom；指物時，相當(dāng)于wh

35、ich。在定語從句中做主語或者賓語，做賓語時可省略。(1) The number of the people that/who come to visit the city each year rises one million.(2) Where is the man that/whom I saw this morning?5. whose通常指人，也可指物，在定語從句中做定語(1) He has a friend whose father is a doctor.(2) I once lived in a house whose roof has fallen in. Whose指物時，

36、常用以下結(jié)構(gòu)來代替(3) The classroom whose door is broken will soon be repaired.(4) The classroom the door of which is broken will soon be repaired.(5) Do you like the book whose color is yellow?(6) Do you like the book the color of which is yellow?注意介詞+關(guān)系代詞引導(dǎo)的定語從句關(guān)系代詞在定語從句中做介詞賓語時從句常由介詞+關(guān)系代詞引導(dǎo)(1) The school (

37、that/which) he once studied in is very famous.(2) The school in which he once studied is very famous.(3) Tomorrow I will bring here a magazine (that/which) you asked for.(4) Tomorrow I will bring here a magazine for which you asked.(5) Well go to hear the famous singer (whom/that/who)或主句的某一部分 2.當(dāng)先行詞

38、是專有名詞或物主代詞和指示代詞所修飾時，其后的定語從句通常是非限制性的，例如：Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了，他曾經(jīng)是我的老師。My house, which I bought last year, has got a lovely garden.我去年買的的那幢房子帶著個漂亮的花園。 This novel, which I have read three times, is very touching. 這本小說很動人，我已經(jīng)讀了三遍。3.非限制性定語從句還能將整個主句

39、作為先行詞, 對其進(jìn)行修飾, 這時從句謂語動詞要用第三人稱單數(shù)，例如：He seems not to have grasped what I meant, which greatly upsets me. 他似乎沒抓住我的意思，這使我心煩。Liquid water changes to vapor, which is called evaporation. 液態(tài)水變?yōu)檎羝@就叫做蒸發(fā)。4. 有時as也可用作關(guān)系代詞5. 在非限定性定語從句中，不能用關(guān)系副詞why和關(guān)系代詞that，而用who, whom代表人，用which, whose代表事物.；關(guān)系代詞引導(dǎo)的定語從句1.who指人在從句中

40、做主語(1) The boys who are playing football are from Class One.(2) Yesterday I helped an old man who lost his way.2. whom指人，在定語從句中充當(dāng)賓語，?？墒÷浴＃ㄗⅲ簑ho和whom已無太大區(qū)別，可以通用。）(1) Mr. Liu is the person (whom) you talked about on the bus.(2) Mr. Ling is just the boy whom I want to see.(3) The man who/whom you met j

41、ust now is my friend.注意：關(guān)系代詞whom在口語和非正式語體中常用who代替，可省略。如果在從句中做賓語,就用whom或who.比如: He is the man whom/who I talk to. 如果是在從句中作主語就只能用who.比如: He is the man who has an English book.3.which指物，在定語從句中做主語或賓語，做賓語時可省略(1) Football is a game which is liked by most boys.(2) This is the pen (which) he bought yesterda

42、y. 4. that指人時，相當(dāng)于who或者whom；指物時，相當(dāng)于which。在定語從句中做主語或者賓語，做賓語時可省略。(1) The number of the people that/who come to visit the city each year rises one million.(2) Where is the man that/whom I saw this morning?5. whose通常指人，也可指物，在定語從句中做定語(1) He has a friend whose father is a doctor.(2) I once lived in a house

43、 whose roof has fallen in. Whose指物時，常用以下結(jié)構(gòu)來代替(3) The classroom whose door is broken will soon be repaired.(4) The classroom the door of which is broken will soon be repaired.(5) Do you like the book whose color is yellow?(6) Do you like the book the color of which is yellow?注意介詞+關(guān)系代詞引導(dǎo)的定語從句關(guān)系代詞在定語從句

44、中做介詞賓語時從句常由介詞+關(guān)系代詞引導(dǎo)(1) The school (that/which) he once studied in is very famous.(2) The school in which he once studied is very famous.(3) Tomorrow I will bring here a magazine (that/which) you asked for.(4) Tomorrow I will bring here a magazine for which you asked.(5) We will go to hear the famou

45、s singer (whom/that/who)賓、定、狀)，也能正確選擇出關(guān)系代詞/關(guān)系副詞。例1. Is this museum _ you visited a few days ago?A. whereB. thatC. on whichD. the one例2. Is this the museum _ the exhibition was held?A. whereB. thatC. on whichD. the one答案：例1 D，例2 A例1變?yōu)榭隙ň洌?This museum is _ you visited a few days ago.例2變?yōu)榭隙ň洌?This is t

46、he museum _ the exhibition was held. 在句1中，is后應(yīng)跟表語，只有the one可以，而后面的you visited a few days ago則做one的定語從句。而句2中, 主、謂、賓俱全，從句部分為句子的狀語表地點，既可用副詞where，又因 in the museum詞組，可用介詞in + which 引導(dǎo)地點狀語。而此題中，介詞on 用的不對，所以選A。關(guān)系詞的選擇依據(jù)在從句中所做的成分，先行詞在從句中做主、定、賓語時，選擇關(guān)系代詞 (who, whom, that, which, whose)； 先行詞在從句中做狀語時，應(yīng)選擇關(guān)系副詞 ( w

47、here 地點狀語，when 時間狀語，why 原因狀語)介詞+關(guān)系詞1）介詞后面的關(guān)系詞不能省略。2）that前不能有介詞。3） 某些在從句中充當(dāng)時間，地點或原因狀語的"介詞+關(guān)系詞"結(jié)構(gòu)可以同關(guān)系副詞when ,where和why 互換。This is the house in which I lived two years ago.This is the house where I lived two years ago.Do you remember the day on which you joined our club?Do you remember the d

48、ay when you joined our club? This is the reason why he came late. This is the reason for which he came late.（八）先行詞和關(guān)系詞二合一1)Whoever spits in public will be punished here. (Whoever 可以用 anyone who 代替)2)The parents will use what they have to send their son to technical school. (what 可以用all that代替) （九）as

49、, which引導(dǎo)的非限定性定語從句由as, which 引導(dǎo)的非限定性定語從句，as和which可代整個主句，相當(dāng)于and this或and that。As一般放在句首，which在句中。As we know, smoking is harmful to one's health. The sun heats the earth, which is very important to us.典型例題1）Alice received an invitation from her boss, _came as a surprise. A. itB. thatC. whichD. he答案

50、C. 此為非限定性從句，不能用 that修飾，而用which.，it 和he 都使后句成為句子，兩個獨立的句子不能單以逗號連接。況且選he句意不通。2）The weather turned out to be very good, _ was more than we could expect. A. whatB. whichC. thatD. it答案B。which可代替句子，用于非限定性定語從句，而what不可。That 不能用于非限定性定語從句，it不為連詞，使由逗號連接的兩個句子并在一起在英語語法上行不通。3）It rained hard yesterday, _ prevented

51、me from going to the park. A. thatB. whichC. asD. it答案B. as 和which在引導(dǎo)非限制性定語從句時，這兩個關(guān)系代詞都指主句所表達(dá)的整個意思，且在定語從句中都可以作主語和賓語。但不同之處主要有兩點：(1） as 引導(dǎo)的定語從句可置于句首，而which不可。(2） as 代表前面的整個主句并在從句中作主語時，從句中的謂語必須是系動詞；若為行為動詞，則從句中的關(guān)系代詞只能用which.。 在本題中，prevent由于是行為動詞，所以正確選項應(yīng)為B。As 的用法例1. the same as；suchas 中的as 是一種固定結(jié)構(gòu), 和一樣。I

52、 have got into the same trouble as he (has).例2. as可引導(dǎo)非限制性從句，常帶有'正如'。As we know, smoking is harmful to one's health.As is known, smoking is harmful to one's health.As是關(guān)系代詞。例1中的as作know的賓語；例2中，它充當(dāng)從句的主語，謂語動詞know要用被動式。 一、“as / which” 特殊定語從句的先行成分1. 形容詞或形容詞短語作先行成分, 具有形容詞意義的介詞短語也可以充當(dāng)先行成分，如：M

53、y grandmothers house was always of great importance to me, as my own is.在一定的語言環(huán)境里，有些名詞可以具有形容詞的性質(zhì)。這些名詞主要是那些表示人的身份、職業(yè)、狀態(tài)的名詞。值得一提的是，在這些具有形容詞性質(zhì)的名詞之后，引導(dǎo)定語從句的關(guān)系代詞不能用who / whom.2. 動詞短語先行成分這種動詞短語既可是限定形式也可是非限定形式。如果是動態(tài)動詞短語，它們在從句中就一般有限定或非限定形式的替代動詞do和as / which一起代替。do可以出現(xiàn)，也可以不出現(xiàn)，但不能用其它動詞代替。3. 句子作先行成分這句子可以是整個主句也

54、可以只是主句中的一個從句。有時是連續(xù)幾個句子，有時甚至可以是一個完整的故事。二、“as/which”特殊定語從句在句中的位置由于先行成分的構(gòu)成成分不同，“as/which”特殊定語從句在句中的位置有以下幾種情況：1. 形容詞做先行成分時：形容詞或形容詞短語（含具有形容詞性質(zhì)的名詞）作先行成分，“as / which”特殊定語從句置于先行成分之后。2. 動詞短語作先行成分時：動詞短語作先行成分時，“as / which”特殊定語從句置于先行成分之后。但是，當(dāng)從句中含有表示主觀意志的插入成分時，“as”特殊定語從句可以移至句子之首。3. 句子作先行成分時：“as”特殊定語從句的位置較靈活，可以置于

55、先行成分之前、之中或之后。但如果先行成分是直接引語，“as”特殊定語從句多在先行成分之前。如果先行成分是否定句，“as”特殊定語從句與否定詞的相對位置不同可以使它產(chǎn)生不同的意義。由于“as”特殊定語從句具有這一特點，所以有時它的位置不能隨便移動。在非正式的文體里，“which”特殊定語從句可以出現(xiàn)在先行成分之中。三、“as/which”特殊定語從句的語義功能一般說來，as與which的語義功能相同，可以相互替換。但先行成分為句子時，它們的語義功能則有差異。1. 表示結(jié)果表示結(jié)果的特殊定語從句與其先行成分之間存在著一定的因果關(guān)系，從句中往往使用有結(jié)果意義的詞，如動詞result, make, enable, cause和形容詞interesting, surprising, delightful, disgraceful等。2. 表示評注表示評注的特殊定語從句對其先行成分所述事實的正確性有肯定的傾向，它通常與那些表示客觀事實，普遍真理或某種習(xí)性的先行成分連用；從句中則常用一些表示“合乎自然規(guī)律”“眾所周知”或“經(jīng)常發(fā)生”等意義的詞語，如natural, known to all, usual等。3. 有無狀語意義 “as”特殊定語從句具有狀語意義（主要是方式狀語意義），而“wh