条件状语从句

初中英语――条件状语从句一．if引导的条件状语从句引导条件状语从句最常用的连词是if，常见的if条件状语从句表示在某条件下，某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如：Ifyouaskhim，hewillhelpyou．如果你请他帮忙，他会帮你的。Ifyoufailintheexam，youwilllethimdown．如果你考试不及格，你会让他失望的。Ifyouhavefinishedthehomework，youcangohome．如果你作业做完了就可以回家了。另外，if从句还表示不可实现的条件或根本不可能存在的条件，也就是一种虚拟的条件或假设。从句多用一般过去时或过去完成时，表示对现在或过去的一种假设。如：IfIwereyou，Iwouldinvitehimtotheparty．如果我是你，我会邀请他参加聚会。IwouldhavearrivedmuchearlierifIhadnotbeencaughtinthetraffic．要不是交通堵塞，我本会来得早一些。另外你还要注意if条件句的时态搭配1．if从句用一般现在时，主句用一般将来时Ifheruns,he’llgetthereintime.如果他用跑的，他就会及时赶到那儿。Thecatwillscratchyouifyoupullhertail.如果你拉猫的尾巴，它就会抓你。2．if从句用一般现在时，主句用may/might/canIfthefoggetsthicker,theplanemay/mightbediverted.如果雾在大一些，飞机可能就会改在别的机场降落。Ifitstopssnowing,wecangoout.如果雪停了，我们就可以出去。3．if从句用一般现在时，主句用must/shouldIfyouwanttoloseweight,youmust/shouldeatlessbread.如果你想减肥，你必须少吃面包。4．if从句用一般现在时，主句用一般现在时Ifyouheatice,itturnstowater.(也可用willturn)如果把冰加热，它就会化成水。5．if从句用现在进行时，主句用一般将来时IfyouarelookingforPeter,you’llfindhimupstairs.如果你是在找彼得，上楼就会找到他。6．if从句用现在完成时，主句用一般将来时Ifyouhavefinisheddinner,I’llaskthewaiterforthebill.如果你吃完了，我就叫服务生来算账注意：学习if引导的条件状语从句的用法,现在总结一下:if条件句不一般,几个要点记心间;条件句,放在前,逗号要放句中间。条件句表可能，主句多用将来时；条件句表事实，主句常用现在时。在if引导的条件状语从句中，如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。如：Wecanwalkthereifwecan'tfindabus.Ifitrainstomorrow,wewillnotgotothezoo.Whatwillyoudoifyoufindapandaindanger?如果if条件句谈论的是重复发生和预示要发生的情景和事件，则主从句大多用一般现在时态。如：Ifbearsareindanger,theyattackpeople.在if引导的条件状语从句中，if和条件句位置灵活，可直接放在主句后面，若if条件句放句首，从句后面要加逗号，和主句隔开。还要注意前后时态一致原则补充：“祈使句+and(or)+陈述句”在意思上相当于一个带有条件状语从句的复合句。Hurryup,oryou’llbelate.→Ifyoudon’thurryup,you’llbelate.Studyhardandyouwillpasstheexam.→Ifyoustudyhard,youwillpasstheexam.二.unless引导的条件状语从句unless的意思是如果不，除非。可与if...not互换。YouwillfailinEnglishunlessyouworkhard.你英语考试会不及格的，除非你更加努力。同义句转换：_________________,oryouwillfailinEnglish.YouwillfailinEnglish_________________________workhard.三.as/solongas引导的条件状语从句as/solongas意思是“只要”Solongasyou'rehappy,Iwillbehappy.只要你高兴，我就高兴。四.once引导的条件状语从句once引导的条件状语从句，意为“一旦...，就”，从句可置于主句前或后Onceyoubegin,neverstop.一旦开始，就绝不要停止Mathsiseasytolearnonceyouunderstandtherules.一旦你理解了规则，数学就不难学了。提示：在条件状语从句中，用一般现在时代替一般将来时，用一般过去时代替过去将来时。Iftheweatherisbadnextweek,we'llputofftheclimbing.如果下周天气不好，我们将推迟爬山。FathertoldmeifIworkedhardhewouldbuymeagift.爸爸告诉我，如果我努力学习，他会给我买一份礼物。五、if条件状语从句的时态练习I.用所给词的适当形式填空1.Ifyou________(feel)tired,you_______________(have)tohavearest.2.Where_______he_________(see)thefilmifhe________________(have)time?3.Ifthere__________(be)fewertrees,there_______________(be)morepollution.4.He_____________(dress)morecasuallyifhe________________(notwork)onweekends.5.IfMarcia_____________(live)alone,she________________(keep)apetparrot.6.Lana_________(buy)anewdressiftheoldone____________(be)outofstyle.7.Thetwins______________(fight)ifthey_______________(argue).8.I____________(have)abakesaleifI_____________(need)moneyforeducation.9.Peter_________(send)meabeautifulsouvenirifhe___________(tour)Spain.10.IfMrGreen______(say)Iamhard-working,myparents_________(feel)glad.11.I____________(go)tothebeachifit________________(notrain)thisweek.12.__________they__________(have)amatchiftheP.E.teacher_____________(be)busy?13.He____(write)alettertohisgrandparentsifhe____(get)hisreportcardthisweek.14.Ifshe____________(get)uplate,she_____________(notcatch)theearlybus.15.Peter________(major)inEnglishifhe____(pass)theexamsinPekingUniversity.II.单项选择1.Ifyou_____totheparty,you’llhaveagreattime.A.willgoB.wentC.goD.going2.Itwillbealongtime____Peter_____hiswork.A.since,hasfinishedB.after,finishesC.when,willfinishD.before,finishes.3.Whatwillfather_____usfromJapan?A.takeB.bringC.carryD.make4.Weifangisfamous______kites.A.forB.toC.onD.with5．I____hertheanswerifshe____me.A.cantell,willaskB.willtell,willaskC.wouldtell,askD.willtell,asks6.–Whatareyougoingtodotomorrow?--We’llgotothelibrarytomorrowifit___.A.isn’trainB.rainC.won’trainD.doesn’train7.—Doyouknowwhenhewillcomebacktomorrow?--Sorry,Idon’tknow.Whenhe____back,I’lltellyou.A.comesB.willcomeC.comeD.maycome8.Whatwillyoudoifyou_____totheoldfolk’shomevisit?A.goB.wentC.goingD.willgo9.IfIeat____food,I’llbeveryfat.A.toomanyB.manytooC.toomuchD.muchtoo10.I’llgivethebooktohimifhe___herenextSunday.A.willcomeB.comesC.iscomingD.came11.There____anEnglishfilminourschooltomorrow.A.isgoingtohaveB.willhaveC.isgoingtobeD.has12.Couldyoutelluswhere____？A.willthenextOlympicGamesheldB.thenextOlympicGameswillbeheldC.wouldthenextOlympicGamesbeheldD.thenextOlympicGameswouldbeheld13.Whenmymotherreturnedlastnight,I____abook.A.readB.amreadingC.wasreadingD.amgoingtoread14.What____you____whenitbegantorain?A.do,doB.were,doingC.are,doingD.did,do15.I’llwakeyouupwhenhe____back.A.willB.isgoingtocomeC.comesD.come