if條件狀語從句及其時態(tài)的用法

if條件狀語從句及其時態(tài)的用法英國前首相撒切爾夫人〔MargaretThatcher〕曾用if條件句對男人和女人進(jìn)行評價：Inpolitics,ifyouwantsomeonetomakeaspeech,askaman;ifyouwantsomethingdone,askawoman.1精選ppt一、概念

連詞if的意思是“如果〞，它引導(dǎo)的句子表示某事發(fā)生所需要的條件，即“在……條件下某事才能發(fā)生〞，在句子中充當(dāng)狀語，因此我們稱之為條件狀語從句。在復(fù)合句中連詞if引導(dǎo)的句子為從句，被修飾的句子為主句。從句可以放在主句后，也可以放在主句前，從句放在主句前時，應(yīng)用逗號將它與主句隔開。例如：We’llgototheGreatWallifitdoesn’traintomorrow.=Ifitdoesn’traintomorrow,we’llgototheGreatWall.2精選ppt二、用法1.條件狀語從句通常由連詞if引導(dǎo)，意為“如果，假設(shè)〞，主句不能用begoingto表示將來，而應(yīng)該用shall或will。例如：IfI’mfreetomorrow,I’llgowithyou.2.if引導(dǎo)的條件狀語從句，主句用一般將來時，從句那么用一般現(xiàn)在時，即“主將從現(xiàn)〞。例如：Ifitissunnytomorrow,I’llclimbthehill.3精選ppt3.正確區(qū)分if引導(dǎo)的條件狀語從句和if引導(dǎo)的賓語從句：在條件狀語從句中，if表示“如果〞；而在賓語從句中，if表示“是否〞。可以用下面的方法區(qū)分：1)從句前置法：if引導(dǎo)的條件狀語從句，可以放在主句之前并用逗號隔開，也可放在主句之后；而if引導(dǎo)的賓語從句只能放在主句之后。因此如果把if放在主句之前，句子通順，意義不變，那么是條件從句，否那么是賓語從句。例如：Hewillhelpyouifyouaskhim.=Ifyouaskhim,hewillhelpyou.4精選ppt2)whether替換法：if引導(dǎo)賓語從句時，其意為“是否〞，通常可用whether替換，意義不變，而if引導(dǎo)條件狀語從句時不能用whether替換。因此，可用whether替換的是賓語從句，不能替換的是條件從句。例如：Iwanttoknowifyouwillgotomorrow.=Iwanttoknowwhetheryouwillgotomorrow.注意：區(qū)分if的用法有著極為重要的意義，因?yàn)樵跅l件狀語從句中，主句用將來時，從句用一般現(xiàn)在時；而在賓語從句中，當(dāng)主句是一般現(xiàn)在時，從句可用所需的任何時態(tài)，主句是一般過去時，從句用過去的某種時態(tài)。5精選ppt穩(wěn)固練習(xí)一、單項(xiàng)選擇1.Ifyou____________totheparty,you’llhaveagreattime.A.willgoB.wentC.goD.going2.I____________hertheanswerifshe____________me.A.cantell,willaskB.willtell,willaskC.wouldtell,askD.willtell,asks3.—Whatareyougoingtodotomorrow?—We’llgotothelibrarytomorrowifit____________.A.isn’trainB.rainC.won’trainD.doesn’train4.—Doyouknowwhenhewillcomebacktomorrow?—Sorry,Idon’tknow.Whenhe____________back,I’lltellyou.

A.comesB.willcomeC.comeD.maycome6精選ppt5.I’llgivethebooktohimifhe____________herenextSunday.A.willcomeB.comesC.iscomingD.came6.There____________anEnglishfilminourschooltomorrow.A.isgoingtohaveB.willhaveC.isgoingtobeD.has7.I’llwakeyouupwhenhe____________back.A.willB.isgoingtocomeC.comesD.come

8.Thefootballmatchwillbeputoffifit____________.

A.willrain

B.rains

C.rained

D.israined

9.There____________abasketballgamethisafternoon.A.isgoingtohave

B.willbe

C.isgoingtoplayD.willplay

10.Iwon’tgoifit____________tomorrow.

A.rain

B.israining

C.rains

D.willrain7精選ppt二、用所給詞的適當(dāng)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精選ppt8.I________(have)abakesaleifI________(need)moneyforeducation.9.Peter________(send)meabeautifulsouvenirifhe________(go)toSpain.10.IfMr.Green________(say)Iamhard-working,myparents________(feel)glad.11.I________(go)tothebeachifit________(notrain)thisweek.12.________they________(have)amatchiftheP.E.teacher________(be)notbusy?13.He________(write)alettertohisgrandparentsifhe________(get)hisreportcardthisweek.14.Ifshe________(get)uplate,she________(notcatch)theearlybus.15.Peter________(major)inEnglishifhe________(pass)theexamsinPekingUniversity.9精選ppt三、完成句子1.如果他遲到了，會發(fā)生什么事情？What_______________ifhe_______late?2.如果努力學(xué)習(xí)，你就會取得好成績。Ifyou______________,you______________good_______.3.他如果看電視太久了，他的父母會不快樂。Ifhe_______TVtoomuch,hisparents______________unhappy.4.如果我們?yōu)樗e辦生日聚會，大家都會來的。Everyone______________ifwe_______abirthdayparty_______him.10精選ppt5.如果明天不下雨，我會和你一起去公園的。Ifit______________tomorrow,I_______gotothepark_______you.6.如果她睡過頭了，就會誤了開會的。She____________________________themeetingifshe______________.7.如果他有空，他會幫助你的。Ifhe______________,he______________