1、 主語從句一、概述：在句子中起名詞作用的各種從句統稱為名詞性從句。根據它們在句中的語法作用，這類從句又可分為主語從句、同位語從句、表語從句和賓語從句。二.主語從句主要有三類：（1）由連詞that引導的主語從句:引導詞that無含義，在句中不做成分，不可以省。例如：Thatyouwillwinthemedalseemsunlikely.你想獲得獎牌看起來是不可能的。Thatyouaresoindifferentbothersme.你如此冷淡使我很煩惱。Thatshesurvivedtheaccidentisamiracle.她在事故中幸免于難簡直是奇跡。（2）用連詞whether引導的主語從句:

2、whether有含義（是否），在句中不做成分，不可以省。例如：Whethersheiscomingornotdoesntmattertoomuch.她來不來都無關緊要。（3）用連接代詞引導的主語從句（在由連接代詞who,whose,whom,which,what,whoever,whomever,whichever,whatever引導的名詞性從句中，其連接代詞在句中起名詞性作用，擔當一定成分）.例如：Whatyouneedismorepractice.你所需要的是更多的訓練。WhatIwanttoknowisthis.我想知道的就是這事。Whateverwedoistoservethepeo

3、ple.我們無論做什么都是為人民服務。（4）用連接副詞when,where,why,how引導的名詞性從句（其連接副詞有含義,在句中作狀語。）eg:Whereweshouldleaveitisaproblem.Whentheywillcomehasntbeenmadepubic.他們什么時候來還不知道。I1I三.注意點:1.it做形式主語,而將主語從句放在句末（尤其是當謂語較短時）。例如：Thatlighttravelsinstraightlinesisknowntoall.光沿直線傳播，這是眾所周知的事。=Itisknowntoallthatlighttravelsinstraightlin

4、es.眾所周知光沿直線傳播。Whentheplaneistotakeoffhasnotbeenannounced.飛機何時起飛還沒有宣布。=Ithasnotbeenannouncedwhentheplaneistotakeoff.還沒有宣布飛機何時起飛。（當what引導的主語從句表示“的東西”時，一般不用it作形式主語。）錯:Itisabookwhathewants.對:Whathewantsisabook.他想要的是本書。例如：Hasitbeensettledwhowillbesenttocarryoutthetask?誰將被派去執行這項任務決定了嗎？固定用法和譯法（1）Itis+名詞+從句

5、Itisafactthat.事實是Itisgoodnewsthat是好消息Itisaquestionthat.是個問題Itiscommonknowledgethat.是常識類似的名詞還有：apity；awonder；agoodthing；nowonder；surprise等。例如：Itisamysterytomehowitallhappened.這一切是怎么發生的是個謎。Itiscommonknowledgethatthewhaleisnotafish.鯨魚不是魚，這是常識。ItisnosurprisethatBobshouldhavewonthegame.鮑勃會贏得這場比賽，這不足為奇。（2

6、）Itis+形容詞+從句Itisnecessarythat有必要Itisclearthat很清楚Itislikelythat很可能Itisimportantthat重要的是類似的形容詞還有：strange;natural;obvious;true;good;wonderful;possible;unlikely;quite;unusual;certain;evident;worth-while;surprising;interesting;astonishing,etc.例如：Itisobviousthatconductorsandinsulatorsarebothimportantinind

7、ustry.很明顯導體和絕緣體在工業中都很重要。Itisdoubtfulwhethershewillbeabletocome.她是否能來令人懷疑。Itwasreallyastonishingthatherefusedtotalktoyou.他拒絕和你說話真是令人驚訝。Itisessentialthatheshouldbeherebytheweekend.周末之前，他應該到這里是必要的。Itseemsobviousthatwecannotgoonlikethis.很明顯我們不能這樣下去了。（3）Itis+過去分詞+從句Itissaidthat據說Itisreportedthat據報道Ithasb

8、eenprovedthat已證明Itmustbeprovedthat.必須扌旨出類似的過去分詞還有：known;estimated;expected;believed;thought;hoped;noted;discussed;required;decided;suggested;demanded;madeclear;foundout,etc.例如：Itisthoughtthatheisthebestplayer.大家都認為他是最好的選手。Itisestimatedthatthevaseis2000yearsold.據估計這個花瓶有2000年的歷史。Itisusedtobethoughttha

9、tanewstarmustbeduetoacollisionbetweentwostars.過去一直認為新星是由于兩顆星星之間碰撞產生的。Ithasnotbeenmadeclearwhenthenewroadistobeopenedtotraffic.還沒弄清楚這條路將開始通車。ItdoesnotmatterifImissedmytrain,becausethereisanotherlater.沒有趕上這趟火車沒有關系，稍晚還有一趟。IthappenedthatIsawhimyesterday.碰巧我昨天看見他了。當“及物動詞+賓語”較短時，也可用這種結構。例如：Itshockedmethat

10、Peterdidnottellanybodywherehewas.讓我吃驚的是彼得沒有告訴任何人他在哪里。Itdoesnotinterestmewhetheryougoornot.我對你去不去不感興趣。2.只用whether不用if引導主語從句.I.選擇題：asmuchasone-fifthofalltimberharvestedisnotused.A.TheestimateB.TheestimateC.TheyareestimatedD.Itisestimatedthatsomemammalscametoliveintheseaisnotknown.A.WhichB.SinceC.Altho

11、ughD.Howwehaveachievedisattributedtotheguidanceofourparents.A.WhoeverB.WhateverC.HoweverD.Thatwealthydoesnotnecessarilymeanthatamanisgreedy.A.ForthereasonthatheisB.JustbecauseheisC.ThereasonofbeingD.Thatheis Althoughhappenedinthisdevelopedcountrysoundslikesciencefiction,itcouldoccurelsewhereinthewor

12、ld.A.whichB.whatC.howD.itshehadforgottentotakehernotebook.A.ThatoccurredtoherB.SheoccurredthatC.ToherthatoccurredD.ItoccurredtoherthatIamsurethatshesaidiswrong.A.whichB.allC.thisD.whatWelostourwayintheforest,andmademattersworsewasthatitwasgettingdark.A.thatB.whichC.itD.whatsomemammalscametoliveinthe

13、seaisnotknown.A.WhichB.SinceC.AlthoughD.Howornotisstilluncertain.A.HescomingB.IfheiscomingC.ThatcomingD.Whetherhescoming11.Itshellbeabletocome.A.doubtwhetherB.doubtfulC.doubtitD.doubtfulwhetherheisatworkintheheartofthebigcityorathomeinthequietsuburb,Dickslifeistiedtomachines.A.WhetherB.TillC.IfD.Unl

14、esshesawbothsurprisedandfrightenedhim.A.ThatB.WhenC.WhatD.Whichisaspellofwarmsunshine.A.Whatdoweallneed.B.WhatallweneedC.WhatweneedD.Whatweallneedisapitythatheshouldfeelsoupset.A.WhatB.ThatC.HeD.It aspoonfulofsoilcantellussomuchaboutthestructureandearlyhistoryofthemoon.A.RemarkableB.QuiteremarkablyC.ItisremarkablethatD.Itisremarkablefactthatyounominatewillbee