主语从句名词性从句包括:主语从句、表语从句、宾语从句和同位语从句。引导名词性从句的连词有:A.连词:that,whether,if(这三个词都不作从句的成分,同时,that无含义,而whether和if都表“是否”)B.疑问代词:who,whom,whose,what,whichC.疑问副词:when,where,why,how(一)主语从句:在复合句中充当主语的从句。1.that引导主语从句that引导主语从句时不同于其他的连词,既无词义也不作成分,只起单纯的连接作用,且通常不可以省。为了强调that引导的主语从句而置之于句首时,that不可省。①Thatthedrivercouldnotcontrolhiscarwasobvious.很明显司机不能控制住他的车了②Thatshewaschosenmadeusveryhappy.她被选上让我们很高兴③Thathewillcomeiscertain.他要来已经千真万确了★通常,that引导主语从句时用it做形式主语,把从句置于句尾,此时that有时可省。例如:①Itwasobviousthatthedrivercouldnotcontrolhiscar.很明显司机不能控制住他②Itmadeusveryhappythatshewaschosen.她被选上让我们很高兴③Itiscertainthathewillcome.他要来已经千真万确了★如果以that从句为主语的句子是疑问句,就只能用先行词it结构。例如:①Isitcertainthathewillcome?②Isittruethathewouldtaketherisk?▲it做形式主语有以下几种不同的结构:(1)It+be+形容词+that-从句①Itislikelythathewillcome.他可能会来②Itisstrangethatshehasevertrustedhim.她相信他,真令人奇怪(2)It+be+名词+that-从句Itiscommonknowledgethatthewhaleisnotafish.鲸鱼并不是鱼,这是常识It'sapitythatheshouldhavecatchedthetrain.(3)It+be+-ed分词+that从句Itissaidthatheisafamouswriter.据说他是个著名作家Itisreportedthattherewillbeastormthisafternoon.据报道下午将有一场暴风▲在表示建议、要求、命令等意义的被动结构中,that从句中的谓语动词常用(should)do。(参见虚拟语气部分)Itissuggestedthatthemeeting(should)beheldthisafternoon.会议被建议在下午举行Itisdemandedthathe(should)leaveatonce.他被要求立即离开(4)It+seem/happen/appear等不及物动词+that从句。Itseemsthatheiswrong.看起来似乎他错了Itappearsthattheyareinneedofhelp.看起来他们需要帮助2.whether引导主语从句,意为“是否”,只起连接作用,不充当任何成分。(置于句首时必须用whether引导,置于句尾时,间或可用if。)Whetherhewillwinthegameisnotclear.他是否会赢得比赛还不清楚。Whetherhewillcomeisuncertain.他是否会来还不确定Itisnotclearwhether/ifhewillcome.Itwasuncertainwhetherhewouldcome.3.连词代词what,who,which,whose等引导的主语从句。这些连接代词作用相当于代词,在从句中担当主语、宾语、表语、定语等。Whatweneedismoretime.我们需要的是更多时间Whowasresponsiblefortheaccidentisnotyetclear.谁应该对这场事故负责还不清楚。Whosebookitisnotimportant.这是谁的书并不重要。Whichschoolyouwanttogomattersmuch.你想去哪所学校很重要4.连接副词when,where,why,how引导的主语从句。这些连接副词相当于副词,在从句中充当状语。Whyhedidthisisnotknown.他为什么做这件事还不知道。Whenhewillcomeisstillunknown.他什么时候来还不知道。Itisnotknownwhyhedidthis.他为什么做这件事还不知道注意:wh-引导的主语从句也常用it作形式主语。5.也可用whatever,whoever,whomever,whenever,wherever等词引导主语从句,表示“无论什么”、“无论谁”、“无论何时”、“无论在(到)哪里”等。Whateverhegaveyoushouldbehandedin.他无论给你什么都要上交Whoevertoldyouthatwaslying.无论谁告诉你,那都是撒谎Whoevercomesiswelcome.无论谁来都是欢迎的