主语从句讲解及其练习

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1、主语从句一、主语从句的连词分三类（1）从属连词引导的主语从句（thatwhetherif）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：Thatyouwillwinthemedalseemsunlikely.Thatshesurvivedtheaccidentisamiracle.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whethe

2、r。Whetherwewillholdapartyintheopenairtomorrowdependsontheweather.Whethersheiscomingornotdoesn’tmattertoomuch.（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：Whatyouneedismorepractice

3、.Whateverwedoistoservethepeople.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=anythingthat;whoever=anyonewho。要注意和whatever,whoever引导的让步状语从句的区别。如：Whoeverbreaksthelawshouldbepunished.（主语从句）（＝Anyonewhobreaksthelawshoul

4、dbepunished.）Whoeverbreaksthelaw,heshouldbepunished.（让步状语从句）（＝Nomatterwhobreaksthelaw,heshouldbepunished.）（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:Whereweshouldleaveitisaproblem.Whentheywillcomehasn’tbeenmadepubic.三、it作形式主语的主语从句有时为了考虑句子平

5、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：Itis+名词+从句Itisafactthat…事实是……；Itisgoodnewsthat………是好消息；Itisaquestionthat………是个问题；Itiscommonknowledgethat………是常识类似的名词还有：apity；awonder；agoodthing；nowonder；surprise等。Itisamystery

6、tomehowitallhappened.Itiscommonknowledgethatthewhaleisnotafish.ItisnosurprisethatBobshouldhavewonthegame.Itis+形容词+从句Itisnecessarythat…有必要……；Itisclearthat…很清楚……；Itislikelythat…很可能……；Itisimportantthat…重要的是……类似的形容词还有：strange;natural;obvious;true;good;

7、wonderful;possible;unlikely;quite;unusual;certain;evident;worth-while;surprising;interesting;astonishing,etc.Itisdoubtfulwhethershewillbeabletocome.Itisessentialthatheshouldbeherebytheweekend.Itseemsobviousthatwecannotgoonlikethis.Itisnecessarythatyou

8、（should）masterthecomputer.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。Itis+过去分词+从句Itissaidthat…据说……；Itisreportedthat…据报道……；Ithasbeenprovedthat…已证明……；Itmustbeprovedthat…必须指出……类似的过去分词还有：known;estimated;expected;believed;thought;hoped;noted;d