在高中英语教学中it用法讲解

1.做形式主语It可以用作先行词作为句子的主语,而把句子的真正主语移到后面去,可以移到后面的主语是：1)不定式句子的谓语可以是be+形容词；e.g.Itisimportanttoknowyourlimitations.知道自己的局限性是很重要的。be+名词；e.g.Itisagoodideatohavealittlenotebookhandy.手边有个小笔记本是个好主意。be+介词短语；e.g.Itisagainstthelawtodothat.这样做是违法的。其他类型的谓语e.g.Itgivesmegreatpleasuretoseethemovie.观看电影让我很高兴。2)动名词用nogood,nouse,greatfun,anewexperience等名词作表语；e.g.Itisfunworkingforhim.为他工作很有意思。也可用某些形容词作表语；e.g.Doyouthinkitisworthwhilequarrellingwithhim？你认为和他吵值得吗？一些其他的谓语形式。e.g.Doesitmatterwastingalittlemoney?稍微浪费一点钱行吗？3)主语从句可以是that引导的；e.g.Itisstrangethatithasn’tbeennoticedbefore.真奇怪,它以前没有引起注意。Itisawonderthatheisstillalive.他居然还活着,真是个奇迹。Ithappenedthattheharvestwasbadthatyear.碰巧,那年的收成不好。ItissaidthattherehasanearthquakeinJapan.据说日本发生了地震。也可能是wh-词引导的e.g.Itisstillaquestionhowmanypeoplearetocome.多少个人会来,还是个问题。ItisnobusinessofyourswhereIspendmysummer.我在哪儿过夏天,这不关你的事。Itremainstobeseenwhetheritwilldousharmorgood.对我们有好处还是有害处,还要等着瞧。Itwasclearenoughwhathemeant.他的意思很清楚。当复合宾语中的宾语是不定式、动名词、宾语从句时,往往把宾语放在它的补足语后面,而用it作形式宾语,放在宾语补足语之前。e.g.Ithinkitnousearguingwithhim.我认为和他争吵没有用。2.作形式宾语。IfounditveryinterestingtostudyEnglish.我发现学英语非常有趣。Hemadeitclearthathewasnotinterestedinthissubject.他非常清楚地表示他对那门学科不感兴趣。3.用于强调结构要强调句子的某一部分,通常是主语、状语、宾语,可以把it当作先行词。这种句子的结构是：“Itis/was+被强调部分+that/who+句子的其他部分”。如果强调的是人,可以用who,whom代替that。e.g.ItisProf.LinwhoteachesusEnglish.(强调主语)ItisEnglishthatProf.Linteachesus(强调宾语)ItwasinShanghaithatIsawthefilm.(强调状语)Itwasin2001thatIwenttouniversity.(强调状语)e.g.Thefrogisnotawarm-bloodanimal.It’sacold-bloodedone.4.用作人称代词代替前文提到的事物。5.作为非人称代词1)起指示代词的作用,指一个人或事物。e.g.—Whoisknockingatthedoor？—It’sme.2)泛指天气。e.g.It’sawarmsunnyafternoon.3)泛指时间e.g.Itwasnearlymidnightwhenshecameback.4)泛指环境e.g.Itisnoisyhere.5)泛指距离e.g.Itishalfanhour’swalktothecitycenter.6.用于某些习语makeit及时赶到;成功;办成e.g.Youcanmakeitifyouhurry.如果你赶快还可以及时赶到。Youneedn’tworry;hewillmakeit.你不必担心,他会办到的。catchit被责骂;受处罚e.g.IfIcomehomelateI’llcatchitfrommymother.如果我回家晚了,我妈妈会骂我。You’llcatchitbecauseofyourcarelessness.你会因为你的不小心受处罚的。7.It的一些习惯用法Howisitwithyourstudy?学习好吗？That’sit.这就对了。Itwenthardwithhim.他身遇不幸。Itisalloverwithme.我完蛋了。Wemustfightitout.我们必须坚持到底。Ican’thelpit.我没有办法。结构Itis(was)+所强调的成分(主语/宾语/状语)+that（it在这种句型中本身无实际意义）注意：1.除谓语动词以外的成分都可用于强调句中;2.如原句时态为现在时或将来时，则be用is,如原句时态为过去时,则be用was;3.当被强调部分为人，引导词还可以用who即:Itis(was)+所强调的成分+who原句：Marydidtheexperimentinthelabyesterdayevening.强调主语：ItwasMarythat/whodidtheexperimentinthelabyesterdayevening.强调宾语：ItwastheexperimentthatMarydidinthelabyesterdayevening.强调时间：ItwasyesterdayeveningthatMarydidtheexperimentinthelab.(注意不用when)强调地点：ItwasinthelabthatMarydidtheexperimentyesterdayevening.(注意不用where)一般疑问句的强调句型：Is/Was+it+被强调的部分+that/who+其余部分?特殊疑问句的强调句型：被强调部分(通常是疑问代词或疑问副词)+is/was+it+that/who+其余部分?原句为特殊问句:Howdidhecomehere?强调how:Howwasitthathecamehere?原句为特殊问句:Whydidhecamelate?强调why:Whywasitthathecamelate?1.我是在街上遇见她的父亲的。(强调在街上)2.你是8点开始工作的吗？（强调时间）3.正是因为她病了，他们才没叫她做这项工作。4.他为什么不能回答这个问题？ItwasinthestreetthatImetherfather.Wasitateighto’clockthatyoubegantowork?Itwasbecauseshewasillthattheydidn’taskhertodothejob.Whywasitthathecouldn’tanswerthequestion？判断是否是强调句，可把Itis/was…that去掉，剩余部分在不增减任何词的情况下还是一个完整的句子，那么这个句子是强调句。ItwasinthestreetthatImetherfather.→InthestreetImetherfather.Itwasbecauseshewasillthattheydidn’taskhertodothejob.→Becauseshewasill,theydidn’taskhertodothejob.not...until...的强调形式是：Itisnotuntil+被强调部分+that...，主要用于强调时间状语的强调句型。Ididn'trealizeshewasafamousfilmstaruntilshetookoffherdarkglasses.→NotuntilshetookoffherdarkglassesdidIrealizeshewasafamousfilmstar.→ItwasnotuntilshetookoffherdarkglassesthatIrealizedshewasafamousfilmstar.not...until...的强调形式原句:Hedidn’tcomeuntil7o’clock.强调not...until:Itwasnotuntil7o’clockthathecame.谓语谓语的强调方式：do/does/did+动词原形我的确相信他是个诚实的人。Idobelievethatheisanhonestman.他们昨天的确去看过你，但没见到你。Theydidgotoseeyouyesterday,butfailedtomeetyou.谓语谓语的强调方式“What+从句+is/was…”是名词性从句结构，常用来强调主语或宾语。他最希望的是成为一名飞行员。Whathewishesmostistobecomeapilot.所叙述的是现在或者将来发生的事情What+从句is…所叙述的是过去发生的事情What+从句was…What+从句+is/was…Whatinterestedmemostwasthebeautifulscenery.给予我们鼓励的是他为我们树立的榜样。Whatencourageduswastheexamplehesetforus.使我最感兴趣的是那美丽的风景。RewriteeachsentencewithItis…that/who…togivemoreemphasistotheunderlinedpart.(page29)1.Itisscientistswhowarnedthatgreenhousegaseswouldwarmtheearthbytrappingheatenergyintheatmosphere.2.Itisthegreenhouseeffectthatgivestheearth’ssurfacetheaveragetemperatureof15ºC.3.Itisfossilfuelsthatmuchoftheenergyusedtolightandheatourhomescomesfrom.4.Itisthedevelopedcountriesthatconsumethemostenergyintheworld.5.Itisforcenturiesthatcarbondioxidehasthetendencytostayintheatmospherewhileothergreenhousegasesstayintheatmosphereonlyforadayorless.6.Itistheirveryexistencethatlow–lyingcountriesfeelisindangerfromrisingsealevels.7.Itisenvironmentalistswhohavetriedtostoptheearth’stemperaturerising.8.Itisfutureclimatechangesandtheireffectsonourenvironmentthatscientistswanttofindoutabout.9.Itisbyseveralmetresthattheleveloftheseacouldriseintheyearsaheadbecauseofglobalwarming.10.Itisouterspacethatmightprovideuswithnewenergysourcesinthefuture.Moreexercises1.Itwas___hesaid____disappointedme.A.what;thatB.that;thatC