条件状语从句 (3)ppt课件

条件状语从句,1,预习：1.什么是条件状语从句？2.条件状语从句如何与主句时态搭配？,2,条件状语从句经典例句：1.Ifyoustickapinintoaballoon,itbursts.2.Unlessyoukeepicecreaminafridge,itmelts.,3,一、什么是条件状语从句？在某种条件下，可能发生某事。而由if/unless引导的表示条件的句子，就叫条件状语从句。eg:Ifyougetupearly,youwillcatchthebus.Ifyouputwoodintowater,itfloats.,4,二、时态1当主句和从句所表示的是原理、客观真理、规则时，主句是一般现在时（包括祈使句和含有情态动词can/may/must等），从句也要用一般现在时。例如：1)Ifyouputapieceofpaperintowater,itgetswet如果你把一张纸放进水中，它会变湿。(原理),5,2)Becarefulifyoucrosstheroad.(祈使句)3)Youmustseethedoctorifyouareill.(含有情态动词）,6,2.在if条件状语从句中，如果从句谈论的是一个可能发生的事实及其产生的相关结果，主句用一般将来时，从句用一般现在时。eg:1)Ifitrainstomorrow,wewillnotgotothezoo.2)Ifyougotobedearlier,youwontfeeltiredinthemorning.,7,3.如果从句用现在进行时或现在完成时，主句需用一般将来时。1）IfyouarelookingforPeteryoullfindhimupstairs.如果你是在找彼得，上楼就会找到他。2）IfyouhavefinisheddinnerIllaskthewaiterforthebill.如果你吃完了，我就叫服务生来算账。,8,三、条件状语在句中的位置大多数情况下，if/unless从句既可以放在主句之前也可以放在主句之后。当从句置于主句之前时，常用逗号与主句隔开。Itfloatsifyouputwoodintowater.=Ifyouputwoodintowater,itfloats.,9,四、转换1、当主语是you时,if引导的条件状语从句可与“祈使句+andor+简单句”进行句型转换。and表示句意顺承；or表示转折，意为“否则”。例如：Takecare,oryoullfalloffthetree.小心，否则你会从树上掉下来。=Ifyoudonttakecare,youllfalloffthetree.,10,2.unless也可引导条件状语从句，相当于if.not，意思是“如果不、除非”。例如：YouwillfailinMathunlessyouworkharder.=YouwillfailinMathifyoudontworkharder.你要是不再加把劲儿，数学考试就不及格了。,11,五、拓展1.if从句还可以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，主句则用虚拟语气。1)IfIwereyou,Iwouldinvitehimtotheparty.2)IwouldhavearrivedmuchearlierifIhadnotbeencaughtinthetraffic.,12,2.if表示“是否”时引导宾语从句，意思同whether.Idontknowifhecancome.Ifhecomes,Illtellyouatonce.,13,一、用括号内单词的适当形式填空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.,14,6.Ifyou_(need)theinstructionsinEnglish,gotoourwebsite.7.Ifthegreenlight_(notbe)on,wemustwaitforoneminute.8.Idontknowifhe_(come)tomorrow.9.Ifyoudontputfishbacktowater,it_(die).10.Dontgoouttomorrowifit_(rain).,15,二、同义句转换1.Playsomesports,andyoullbehealthy._playsomesports,youllbehealthy.2.Ifyoustudyhard,youwillcatchupwithyourclassmates._youstudyhard,youwontcatchupwithyourclassmates.3.Fishwilldiewithoutwater.Fishwilldie_thereisnowater.,16,4.Dontstayuplater,orwontbesleepytomorrow._you_stayuplate,youwontbesleepytomorrow.5.IwillcometoseeyouunlessIamtoobusy._Iam_toobusy,Iwillcometoseeyou.,17,三根据汉语提示完成句子,1.如果我有时间的话，我就会去帮你。IfI_,I_youwithit.2.如果明天不下雨，我们就去徒步旅行。Ifit_tomorrow,wellgohiking.3.我们没有人能赶上汤姆，除非他不跑。Noneofuscan_Tom_hedoestrun.,18,4.他不会迟到的，除非他生病。He_late_he_ill.5.如果你看见汤姆，叫他来我办公室。_Tomtocometomyoffice_you_him.,19,Goodmorning,ladiesandgentlemen!MayIhaveyourattention,please?ImavolunteerandImgladtotellyousomethingaboutprotectingthebeachesinShenzhen.Asweknow,beachesaregreatplacesforustotravelandrelax.Inordertoprotectthebeaches,ourgovernmenthasmadesomestrictrules.However,somecitizensdontunderstandit.,20,Inmyopinion,thesestrictrulescanhelpuscreateabetterbeachenvironment.Thebeacheswillbecleanerandmorebeautifulifeachtouristcanrealizetheimoportanceofprotectingthem.,21,SoIhopeallofuswilltrytofollowthese:Neverthrowrubbisheverywhere.Dontsteponthegrassorpi