,一、時態(tài)如果主句是一般將來時態(tài)，這時從句不可以用將來時態(tài)，而要用一般現(xiàn)在時。例如：Iwontgotherewithyouifitrainstomorrow.如果明天下雨的話，我就不和你一起去那兒了。二、主從句的位置大多數(shù)情況下，從句可以位于主句之前，也可以位于主句之后。不過從句在前時，主從句之間必須用逗號隔開。例如：Pleasetellmeifhecomesback.=Ifhecomesback,pleasetellme.如果他回來了，請告訴我一聲。三、if的兩面性if引導(dǎo)條件狀語從句時意為“如果”，如果引導(dǎo)賓語從句則意為“是否”。請比較：1)Wewillgooutifitisfinetomorrow.2)Idontknowifthetrainhasarrived.句1)中if引導(dǎo)的是狀語從句。這個從句表示“條件”，整個句子的意思是“如果明天天氣好，我們就出去”。句2)中if引導(dǎo)的是賓語從句，充當(dāng)謂語動詞dontknow的賓語，整個句子的意思是“我不知道火車是否到了”。,1.Ifit_sunnytomorrow,I_boating.A.isgoB.willbe,goC.is,willgoD.willbe,willgo2.-Whatwillyoudoifit_tomorrow,-IllstayathomeandwatchTV.A.rainB.rainsC.willrainD.israiningRunfast,oryoullbelateforschool._you_fast,youllbelateforschool.2.Youcanbuythedictionaryifyoutakeenoughmoneywithyou.Takeenoughmoneywithyou,_buythedictionary.3.Ifthereisnoair,noneofuscanlive.Noneofuscanlive_.,If,dont,run,andyoucan,withoutair,if條件狀語從句的時態(tài)練習(xí)1.Diana(willgo/go/goes)toEuropeifshe(willpass/pass/passes)theexams.2.Thegraduates(willteach/teach/teaches)inthepoorvillageiftheteacher(willagree/agree/agrees)soon.3.Ifthere(willbe/are/is)acaraccident,they(willcall/call/calls)110forhelpatonce.4.Ifit(wont/dont/doesnt/isnt)rainy,we(willtake/take/takes)walkoutside.5.IfaUFO(willland/land/lands)infrontofme,I(willgo/go/goes)intolookforthealien.,willgo,passes,willteach,agrees,willgo,lands,willtake,isnt,willcall,is,6.Ifhe(willhave/have/has)money,he(willbuild/build/builds)asciencelab.7.DontwaitformeifI(am/willbe)late.8.They(wont/dont)gotothebeachifit(willrain/rain/rains).9.I(willcall/call)youifhe(willstay/stay/stays)athome.10.Mr.Smith(willlet/let/lets)youknowifhe(willneed/need/needs)help.11.(Will/Do/Does)hevisitthemuseumifhe(wont/dont/doesnt)gettired?12.Where(will/do/does)theyliveifthey(willmiss/miss/misses)thebus?,rains,misses,will,doesnt,Will,needs,willlet,stays,willcall,wont,am,willbuild,has,1.Ifyou_totheparty,youllhaveagreattime.A.willgoB.wentC.goD.going2.Itwillbealongtime_Peter_hiswork.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.cantell,willaskB.willtell,willaskC.wouldtell,askD.willtell,asks,6.Whatareyougoingtodotomorrow?-Wellgotothelibrarytomorrowifit_.A.isntrainB.rainC.wontrainD.doesntrain7.Doyouknowwhenhewillcomebacktomorrow?-Sorry,Idontknow.Whenhe_back,Illtellyou.A.comesB.willcomeC.comeD.maycome8.Whatwillyoudoifyou_totheoldfolkshomevisit?A.goB.wentC.goingD.willgo9.IfIeat_food,Illbeveryfat.A.toomanyB.manytooC.toomuchD.muchtoo10.Illgivethebooktohimifhe_herenextSunday.A.willcomeB.comesC.iscomingD.came,11.There_anEnglishfilminourschooltomorrow.A.isgoingtohaveB.willhaveC.isgoingtobeD.has12.Couldyoutelluswhere_？A.willthenextOlympicGamesheldB.thenextOlympicGameswillbeheldC.wouldthenextOlympicGamesbeheldD.thenextOlympicGameswouldbeheld13.Whenmymotherreturnedlastnight,I_abook.readB.amreadingC.wasreadingD.amgoingtoread14.What_you_whenitbegantorain?A.do,doB.were,doingC.are,doingD.did,do15.Illwakeyouupwhenhe_back.A.willB.isgoingtocomeC.comesD.come,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)a