-Module 12 Unit 3 课件-外研版八年级英语上册

Unit3LanguageinuseModule12HelpThatcouldbeharmful！Betty，youmustknow！Stayawayfromwindowsandheavyfurniture.Donotstandnearstreetlightsorunderpowerlines.仔细观察以上句子的谓语构成，有什么共同规律？Observe概念：祈使句表达说话人对对方的叮嘱、劝告、希望、禁止、建议、请求或命令等。祈使句一般以动词原形开头，无时态和数的变化。祈使句

暗含的主语是you，通常省略。否定句往往由do

not(don’t)或never开头。祈使句的句首或句末有时加please,还可以加上称呼语，用逗号与句子主体隔开。动词原形构成的祈使句Haveaniceday!Don’twasteyourtime!Neverbelateagain!Comethisway,please.Pleasebequiet,boys!Makesurehe’swarm.Don’tusethelift.Let’s

构成的祈使句这类祈使句往往用于提出建议。

a)Let’sspendthisweekendinthecountryside.

b)Let’stakeataxi,shallwe?

在请求、命令和口号中，常用无动词祈使句，实际上是省略了动词，从而使语句更简洁有力。

a)Justaminute,please!b)Thisway,please!无动词祈使句情态动词can和could表示“能够，可以”等意义的用法。还可表示对现在或将来的推测，意为“会，可能”，但can表示推测时，往往用于否定句和疑问句。用于疑问句时，can比could表示的“可能性要大；用于否定句时，can’t表示“不可能”。Youcan’tbeserious!情态动词must/can/could表示推测could则可用于肯定句、否定句和疑问句。在以下例句中,can和could均表示可能:a)Hecouldbeinpain.b)Thatcouldbeharmful!c)Can/Couldthisbetrue?情态动词must也可以表示猜测,意为“一定，准是”，通常只用于肯定句。Betty,youmustknow.—Whosentthepresent?Canitbeyourbrother?(表示不可能)对比下列句子:(询问可能性)—Itmustbeyourbrother.Isawhiminyourroom

justnow.(语气强烈，表示非常肯定)—Itcan’tbemybrother.HeisstillinFrance.1.Itisdangerous.You______keepout!2.Thesestairsarenotsafe.You________usethem.3.Therocksarefallingdown.You______gethit.4.Theriveristoodeep.You_________swiminit.5.Betty______knowwhattodobecauseshedidsomebasicmedicaltraining.mustmustn’tcouldmustn’tmustCompletethesentenceswithcould,mustormustn’t.Exercise用can't，could或must填空1．Thereisachanceofrocksfalling.You__could__gethurt.2．Mary__can't__beathome.Isawherinthelibraryjustnow.3．It__must__beTom’s.Lookathisnameonthecover!4．—Istillhaven'tfoundmypetdog.—I'msorrytohearthat.You__must__beverysad.5．—IsthatmanMr.Zhang?—It__can't__behim.HewenttoBeijingforameetingyesterday.6．—Myhouseisnearabusystreet.—It__can't__beveryquiet.Exercise根据括号内提示完成下列祈使句1．_Don't__speak_(notspeak)withyourmouthfulloffoodand__be__(be)polite.2．__Don't__play_(notplay)toomanycomputergames.3．_Choose_(choose)meandIcanmakemyclassroombeautiful.4．Just_go_(go)straightandturnleft.5．Let's_listen_(listen)tosomesweetmusic，shallwe?6．_Take_(take)yourumbrella,oryou'llcatchacoldonsucharainyday.7．—Sorry，I'mlate.—_Don't_tell_(nottell)methebusbrokedownagain!Exercise1.—Mybrotherwonthefirstprizeinspeechcompetition.—Congratulations!You______beexcitedaboutthat!A.needB.mustC.wouldD.can一、选择题。2.Theladyinthisphoto_____beoverfifty!Shelookssoyoung!A.mustn’tB.mustC.can’tD.canExercise3.ThistoyMickeyMouse______beAmy’s.She’stheonlykidatthepicnic. A.mustB.canC.needD.can’t4.—You___beexcitedthatyou’regoingbacktoyourhometownsoon.—Yes,Ican’twaitanylonger. A.shallB.canC.needD.must5.—Someoneisknocking