GrammarWhatpartdoestheunderlinedpartserveasineachsentence?Atreehasfallenacrosstheroad.Youareastudent.Tofindyourwaycanbeaproblem.Smokingisbadforyou.“Howdoyoudo?”isagreeting.Whatshesaidisnotyetknown.Thatweshallbelateiscertain.Itiscertainthatweshallbelate.MakesentencesIt’scertain.we’llbelate.Ishecomingornot？Wedon’tknowWhatdoeshewanttotellus?Wedon’tknowWhenwillyoucomeback?Itdoesn’tmatter.It’scertainthatwewillbelate.Thatwe’llbelateiscertain.Wedon’tknowwhetherheiscomingornotWhetherheiscomingisnotknown.Wedon’tknowwhathewantstotellus.Whathewantstotellusisnotknown.Whenyouwillcomebackdoesn’tmatter.Itdoesn’tmatterwhenyouwillcomeback.主语从句（NounClausesastheSubject）定义：用作主语的从句叫主语从句，它是名词性从句之一。引导主语从句的连接词有：连词that,whether；连接代词who,what和which；连接副词when,where,how和why。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.连接词：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。Thatshelefthimcuthimtotheheart.Thathewillcomeiscertain.2)连接代词who，what，which,whatever,whichever,whoeverWhatseemseasytosomepeopleseemsdifficulttoothers.Whichsidewillwinisnotclear.由whether及其他连词引导的主语从句放在句首，句后都可。Whetheritwillpleasethemisnoteasytosay.3)连接副词when，where，how，why等。Whyhediditremainsamystery.Whentheywillstartisnotknownyet.Howhebecameagreatscientistisknowntousall.2.位置：主语从句可以前置，也可以后置。用it做形式主语，而把主语从句，在句末，常用下面几种句型。1）It+be+表语+主语从句表语：（名词，形容词，过去分词）Itisstilluncertainwhetherheiscomingornot.ItisanhonourthatIwasinvitedtoattendthemeeting.Itisafact(ashame,apity,goodnews…)that…Itiscertainthatshewilldowellinherexam.ItistruethatItoldhereverything.ItissaidthatMr.GreenhasarrivedinBeijing.ItisreportedthatChinahassentanothermanmadeearthsatelliteintoorbit.2）It+不及物动词+主语从句Itseemed(happened,doesn’tmatter,hasturnedout)that…Ithappensthattheywereabsent.ItseemsthatAliceisnotcomingtothepartyatall.Itdoesn’tmatterwhethershewillcomeornot.Itmakesnodifferencewhereweshallhavethemeeting.3)It+及物动词（被动语态）+主语从句IthasbeendecidedthattheexhibitionwillnotopenonSundays.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：Theyshouldlikeeachotherisnatural.正：Thattheyshouldlikeeachotherisnatural.正：Itisnaturalthattheyshouldlikeeachother.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.误：IfMaryreallyheardhimisreallydoubtful.正：ItwasdoubtfulifMaryreallyheardhim.4).用于Itisimportant/natural/necessary/impossiblethat...句型中,主语从句应使用虚拟语气,谓语动词用\“should+动词原形\”的形式,should有时可以省略。5)在It+be+suggested/advised/ordered/requested/insisted/required中,that从句的谓语也应该用\“should+动词原形\”的形式,should有时可以省略。5.5.主语从句需注意的问题主语从句需注意的问题(1)主语从句中用陈述语序WhatsheisafraidofistheirtakinghertoParis.(Whatissheafraidof…Wrong)(2)主语从句后谓语动词用第三人称单数Thattheyhaven’tphonedisstrange.(3)that引导的主语从句中，that不可被省略Thatpricewillgoupiscertain.6.It6.It作形式主语和作形式主语和itit引导强调句的比较引...
