名词性从句之主语从句

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1、主语从句：做主语用的名词性从句，因其在复合句中做主语，又称主语从句，引导主语从句的有连词that，whether，连接代词who，what，which，连接副词when，where，how，why等。1）从属连词：that，whether等.that引导主语从句只起引导作用，本身无实际意义，在主语从句中不充当任何成分，但不能省略。Thathewillwiniscertain.他肯定会赢。Whetherhe’llcomehereisn’tclear.他是否会来这里还不清楚。注意:由that引导的主语从句有时为了使句子结构平衡,避免“头重脚轻”,常用it作形式主语,而把

2、从句放在后面。例如:1.Thathewillrefusethispieceofadviceisimpossible.~Itisimpossiblethathewillrefusethispieceofadvice2.Thattheyshouldlikeeachotherisnatural.~Itisnaturalthattheyshouldlikeeachother.*it为形式主语这样就构成了下面一些常用句型:1)Itis+n.+从句　Itisapity/shamethat...遗憾的是……　Itisasurprisethat…令人惊奇的是…　Itisafactt

3、hat……是事实Itiscommonknowledgethat……是常识2)Itis+adj.+从句　It’scertainthat…肯定…　Itispossiblethat...很可能……　Itisunlikelythat...不可能……Itisobviousthat…很明显…Itisnecessaryimportantatural...that…3)It+不及物动词+从句Ithappenedthat...碰巧……Itoccurredtomethat…我突然想起…4)It+be+过去分词+从句Itissaidthat...据说……Itisknowntoal

4、lthat...众所周知……Itisreportedthat...据报道……Itisbelievedthat...据信……;人们相信……Itissuggestedthat+(should）do...建议……Itmustbeadmittedthat…必须承认……Itcannotbedeniedthat…不可否认……　　Itmustbepointedoutthat…需指出的是……　2.连接代词who，what，which,whatever,whichever,whoever(Who,whom,which,what可以和ever构成合成词，和what一样引导从句，ever

5、起到强调作用。此类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)Whatmanyscientistsbelieveisthattheearthisround…Whowilltakepartinthemeetinghasnotbeendecided.Whoeverbreaksthelawwillbepunished.Whichstudentwillwinisuncertain.Whateverwassaidheremustbekeptsecret.这里说的话都应当保密。Whoevermakesmistakesmustcorrectth

6、em.凡犯了错误的人都必须改正。3)连接副词when，where，how，why等。Whytheysuddenlydisappearedstillremainsamystery.Whentheywillleaveisnotdecided.Wheresheisfromisunknown.Howwewillpaintthehousehasnotbeendecided.注意:1）主语从句在句首时，必须由连接词引导，不能省略这些连接词；但是如果用it做形式主语，而把主语从句放在句末时，从属连词that可以省略。误：Theyshouldlikeeachotherisnatur

7、al.正：Thattheyshouldlikeeachotherisnatural.正：Itisnatural(that)theyshouldlikeeachother.2)如果主语从句放在句首，不能用if引导，但是如果用it做形式主语，而把主语从句放在句末时，也可以用if引导.或把if改为whether误：IfMaryreallyheardhimisreallydoubtful.正：ItwasdoubtfulifMaryreallyheardhim.正:WhetherMaryreallyheardhimisreallydoubtful.主语从句的规律：例1.W