主语从句的用法.docx

主语从句的用法主语从句定义:在句子中担当主语的是一个从句,这个从句就叫做主语从句。主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。1.It作形式主语和it引导强调句的比较It作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如：Itisapitythatyoudidn’tgotoseethefilm.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。例如：Itisamysterytomehowitallhappened.这一切是怎么发生的是个谜。Itiscommonknowledgethatthewhaleisnotafish.鲸鱼不是鱼，这是常识。ItisnosurprisethatBobshouldhavewonthegame.鲍勃会赢得这场比赛，这不足为奇。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;wonderful;possible;unlikely;quite;unusual;certain;evident;worth-while;surprising;interesting;astonishing,etc.例如：Itisobviousthatconductorsandinsulatorsarebothimportantinindustry.很明显导体和绝缘体在工业中都很重要。Itisdoubtfulwhethershewillbeabletocome.她是否能来令人怀疑。Itwasreallyastonishingthatherefusedtotalktoyou.他拒绝和你说话真是令人惊讶。Itisessentialthatheshouldbeherebytheweekend.周末之前，他应该到这里是必要的。Itseemsobviousthatwecannotgoonlikethis.很明显我们不能这样下去了。Itis+过去分词+从句[1]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;discussed;required;decided;suggested;demanded;madeclear;foundout,etc.例如：Itisthoughtthatheisthebestplayer.大家都认为他是最好的选手。Itisestimatedthatthevaseis2000yearsold.据估计这个花瓶有2000年的历史。Itisusedtobethoughtthatanewstarmustbeduetoacollisionbetweentwostars.过去一直认为新星是由于两颗星星之间碰撞产生的。Ithasnotbeenmadeclearwhenthenewroadistobeopenedtotraffic.还没弄清楚这条路将开始通车。It+不及物动词+从句Itseemsthat…好像是……Ithappenedthat…碰巧……Itfollowsthat…由此可见……Ithasturnedoutthat…结果是……类似的不及物动词还有：seem,appear,occur,follow,happen,turnout,etc.例如：Itturnedoutthatnobodyrememberedtheaddress.结果是无人记得那个地址。Itnowappearsthattheyareinurgentneedofhelp.看起来他们急需帮助。ItdoesnotmatterifImissedmytrain,becausethereisanotherlater.没有赶上这趟火车没有关系，稍晚还有一趟。IthappenedthatIsawhimyesterday.碰巧