精品文档从句一．名词性从句在句子中起名词作用的各种从句统称为名词性从句。这类从句在句中可担任主语、表语、宾语和同位语，名词从句可以分为主语从句、表语从句、宾语从句和同位语从句。1.主语从句在句子中担当主语的是一个句子，这个从句就叫作主语从句。主语从句可以由下列连词、连接代词和连接副词引导，且不能省略。连词：that,whether连接代词：what,whatever,who,whoever等连接副词：when,where,how,why(1)由连词that,whether引导的主语从句连词that,whether在从句中的作用只是引导主语从句，它在从句中不担任成分，不能省略，且由that,whether引导的主语从句，多用it多形式主语e.gThattheearthisroundistrue.=Itistruethattheearthisround.地球是圆的，是一个事实。Whetherhe'llcomeornothasn'tbeendecided.=Ithasn'tbeendecidedwhetherhe'llcomeornot.(2)由连接代词或连接副词引导的主语从句连接代词who,which和连接副词when,where,how,why都可以引导主语从句，它们分别在从句中担任主语、宾语和状语，不能省略，翻译时，不能把它们译为疑问句，由它们引导的主语从句，也可以用形式主语it引导e.gWholetoutthenewsremainedunknown.=Itremainedunknownwholetoutthenews.谁泄漏了那个消息仍旧无人知道。Whenwe'llstartisnotclear.=Itisnotclearwhenwe'llstart.我们何时出发还不清楚。(3)以关系代词what,whatever,whoever,whomever,whichever引导的主语从句不能用形式主语it引导，它们在句子中担任成分，不能省略，语序为陈述语序。e.gWhathesaidatthemeetingisimportant.他在会上所说的事情是重要的。Whoeverleavestheofficeshouldtellme.无论是谁离开办公室都应该告诉我。(4)用it作形式主语的主语从句结构a.Itis+名词+从句Itisafactthat⋯事实是⋯⋯Itisgoodnewsthat⋯⋯⋯是好消息Itisaquestionthat⋯⋯⋯是个问题Itiscommonknowledgethat⋯⋯⋯是常识精品文档．精品文档类似的名词还有：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。b.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。c.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;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.过去一直认精品文档．精品文档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。d.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：Itt...
