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1、名词性从句---主语从句1.Whatisneededforthespacetripiscarefulpreparation.2.Herwishisthatshecanloseweightsoon.3.Ithinkthatwomancanreacheveryhighachievementsinmanyfieldsofscience.4.Wewereveryexcitedatthenewsthatourteamhadwon.引导名词性从句的关联词可分为三类：一．从属连词：that（无任何词意）wheth
2、er,if（均表示“是否”表明从句内容的不确定性）asif,asthough（均表示“好像”，“似乎”）以上在从句中均不充当任何成分二．连接代词：what,who,whom,which，whose,whatever,whoever,whichever(作主宾表定)三．连接副词：when,where,how,why(作状语)I.主语从句1.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。2.位置：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
3、子末尾。3.引导主语从句的关联词：(1)从属连词that,whether,if(在从句中不充当成分，仅起连接作用)ThatJackwonthematchyesterdaysurprisedus.Whetherhe’llcomehereisn’tclear.(此处不能用if)(2)连接代词who,whom,whose,what,which,whoever,whatever,whichever(充当主宾表定)Whatshedidisnotknown.Whoevercomesiswelcome.(3)连接
4、副词where,when,how,why(在从句中充当状语)Howthishappenedisnotcleartoanyone.Whenthemeetingwillbeheldisdecidedbyourmanager.4.有时为了避免头重脚轻，常用it作形式主语，而把真正主语放在句子末尾。Howthebookwillselldependsonitsauthor.=Itdependsonitsauthorhowthebookwillsell.Thatheisthebeststudentinthecl
5、assisobvious.=Itisobviousthatheisthebeststudentintheclass.用it作形式主语的几种常见结构：(1)Itis＋名词＋从句Itisafactthat…事实是…Itisanhonorthat…非常荣幸Itiscommonknowledgethat…是常识(2)Itis＋形容词＋从句Itisnaturalthat…很自然Itisstrangethat…奇怪的是…(3)Itis＋不及物动词＋从句Itseemsthat…似乎…Ithappenedthat…
6、碰巧…Itappearsthat…似乎…(4)It＋过去分词＋从句Itisreportedthat…据报道…Ithasbeenprovedthat…已证实…Itissaidthat…据说…注意：主语从句不可位于句首的五种情况(1)if引导的主语从句不可居于复合句句首。(例子见上面)(2)Itissaid,(reported)…结构中的主语从句不可提前。例如：ItissaidthatPresidentXiwillvisitourschoolnextweek.(3)Ithappens…,Itoccurs
7、…结构中的主语从句不可提前。例如：Itoccurredtohimthathefailedintheexamination.(4)Itdoesn’tmatterhow/whether…结构中的主语从句不可提前。例如：Itdoesn’tmatterwhetherheiswrongornot.(5)含主语从句的复合句是疑问句时，主语从句不可提前。例如：Isitlikelythatitwillrainintheevening?5.语序：主语从句用陈述语序。(关联词位于句首不能省略)Howhebecameag
8、reatscientistisknowntousall.Whothewatchbelongstoisunknown.Thathefinishedwritingthecompositioninsuchashorttimesurprisedusall.6.主语从句中注意的事项：1）主语从句后的谓语动词一般用单数。Whateverhesaysisofnoimportance.Whoeversaysthisiswrong.但谓语动词用单数还是复数，不可一概而论，而要视句子的意
