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Unit4Breakingboundariesit作形式主语[观察例句]1．ItisdifficultforaforeignertolearnChinese.2．It'skindofyoutohelpme.3．Itisnousetalkingtohimaboutit.4．Itisamysterytomehowitallhappened.5．Itisbelievedthatthefloodthereisthebiggestin100years.[归纳用法]it作形式主语时没有具体的意义，只是帮助把真正的主语移到句子后面去，使句子显得平衡。it作形式主语时，真正的主语通常是不定式短语、ing短语或主语从句。一、不定式短语作真正的主语，常用于下列句型中：It＋be＋形容词＋(for/ofsb.)todosth.It＋be＋名词＋todosth.Ittakessb.sometimetodosth.干……花了某人……时间It'suptosb.todosth.干……是某人的职责或义务Itiseveryone'sdutytoobeythelaw.遵守法律是每个人的义务。Ittookthemayeartobuildthebridge.建这座桥花了他们一年的时间。Itisbadmannerstostareatpeople.盯着人看是不礼貌的。Itisuptoustohelpthoseinneed.帮助那些有困难的人是我们的责任。[名师点津]在“It＋be＋形容词＋for/ofsb.todosth.”句型中，如果形容词描述的是sb.，则应用介词of；如果描述的是todosth.就用for。It'snecessaryforustouseashortwaveradiotopickuptheprogrammes.我们用一台短波收音机收听这些节目是必要的。It'simportantforustolearnEnglishwell.学好英语对我们来说是重要的。Itwasfoolishofhimtogiveupthejob.(＝Hewasfoolishtogiveupthejob.)他放弃那工作是愚蠢的[即学即练1]用所给词的适当形式填空①Itisnotuptoyoutotell(tell)mehowtodomyjob.②Itisnotrighttouse(use)theseplacesasrubbishdumps.③Itwasniceofthemtoinvite(invite)us.二、ing短语作真正主语的情况远不及不定式短语那么普遍，常限于nogood,nouse,useless,waste等词的后面。Itisnogood/usehavingacarifyoucan'tdrive.有车如果不会开是没有用处的。ItisawasteoftimewatchingTV.看电视是浪费时间的。Itisnouseaskinghim.问他没有用。[即学即练2]用所给词的适当形式填空①It'snogoodtaking(take)overtheexperienceofforeigncountriesuncritically.②It'snousecrying(cry)overspiltmilk.③Itisworthmaking(make)anappointmentbeforeyougo.三、用it作形式主语，主语从句作真正主语的常见句型有：1．Itisapity/ashame/afact/anhonour/goodnews/nowonder/awonder...that...Itwasapitythattheengineercouldn'tcome.可惜工程师没能来。Itisawonderthathecontinuestogamblewhenhealwaysloses!令人惊讶的是他一直输还一直赌。(Itis)nowonder(that)youwerelate!难怪你来晚了！Itisashamethattherainspoiledourpicnic.真可惜，这场雨把我们的野餐给搅了。ItisafactthatEnglishisbeingacceptedasinternationallanguage.英语被认为是国际语言，这是一个事实。2．Itis＋形容词(如：strange/natural/surprising/obvious/true/fortunate/wonderful/funny/possible/impossible/likely/unlikely/clear/unusual/certain/important...)＋that...Itiscertainthathewillwin.他一定会取胜。Itisimportantthatweshouldlearnfromeachotherandhelpeachother.我们应当互相学习，互相帮助，这是很重要的。Itwasobviousthatthechildhadbeenbadlytreated.很显然那个孩子受过虐待。Itislikelythathewillringmetonight.他今晚可能给我打电话。Itisdoubtfulwhethershewillbeabletocome.她能否来还很难说。3．Itseems/happened/turnedout/suddenlystruckme/occurredtome...that...IthappenedthatIwasn'ttherethatday.恰好那天我不在那里。Itseemsthathisideaismorepractical.看起来他的意见更实际一些。4．It＋be＋过去分词(如：said/reported/announced/decided/expected/hoped/known/believed...)＋that...Itishopedthatthenumberofdeerwillgreatlyincreaseverysoon.(＝Peoplehopethatthenumberofdeerwillgreatlyincreaseverysoon.)人们希望鹿的数目会很快增加。Itisreportedthatmorethantwentypeoplewerekilledinthatbusaccident.据报道在那次的公共汽车事故中有二十多人丧生。[即学即练3]用适当的代词填空①Itisknownthatheisoneofthebestteachersinourschool.②ItsuddenlyoccurredtomethatIknewhowtosolvethatproblem.③Itisstrangethatheshouldhaveleftwithouttellingus.Ⅰ.单句语法填空1．Itisverykindofyoutogive(give)meahandintime.2．Itisstillamysterywhatcausedtheaccident.3．Itisnecessarythatone(should)master(master)theskillsofoperatingcomputer.4．ItisknowntoallthatthegunpowderwasfirstinventedbytheChinese.5．Itseemedcertainthathewillwintheprize.Ⅱ.短文语法填空I1.havestudied(study)Englishforsixyears.Itwasdifficultforme2.toremember(remember)newwordsfirst.Itriedeverymeans,butitnouse3.reciting(recite)themoverandoveragain.Itwasverykindofyou4.tooffer(offer)mesomesuggestions.Itisnecessary5.tounderstand(understand)itsmeaninginsentences.Itisnowonder6.thatyourEnglishisgood.Itisrequested7.thateveryoneshouldmasterpropermethodsoflearning.8.ItwasashamethatIhadn'taskedyouforhelpearlier.IwilltrymybesttoimprovemyEnglish.9.ItishopedthatIwillpasstheTOEFLandhaveachancetostudyabroad.Thanksforyourhelp.Iwouldbegrateful10.ifyoucouldgivemeareplysoon.