高中英语——情态动词2.ppt

GrammarModalVerbs(II)1.a.oughtto“应该”与should的意思大致相同，但should注意表示主观的看法,而oughtto则反映客观情况(义务或责任),比should的语气更重。You_______stayathomeinsuchabadweather.I______workhard.oughttoshouldGrammarb.表示劝告、建议或命令时，should=oughtto，但在疑问句中常用should。oughtto的否定式为oughtn’tto/oughtnotto。Youshould/oughttogotoclassrightaway.ShouldIopenthewindow?Whatshouldwedonext?should和oughtto后面跟动词不定式的完成式,其肯定句表示“过去应该做而未做”,其否定句则表示”过去不该做但做了”。Youshould/oughttohavemadethedecisionaweekago.Ishouldnthavemadesuchafoolishmistake.多数情况下，oughtto可与should互换使用。oughtto的反意疑问句多用oughtn’t替代shouldn’t(美式英语)注意YououghttohavehelpedhimwithhisEnglish,________?A.won’tyouB.oughtn’tyouC.shouldn’tyouD.wouldn’tyou2.must和havetomust的用法?1）表示主观的义务和必要,?主要用于肯定句和疑问句；由must引起的疑问句，肯定回答要用must或have?to,?否定回答要用needn’t或don’t?have?to,?意思是“不必”；must的否定形式mustn’t表示禁止，意思是“不能，不许”。—Must?I?finish?the?task?right?now??

—Yes,?you?must.?/?Yes,?you?have?to.??—No,youneedn’t./No,youdon’thaveto.Youmustn’tcomeherewithoutpermission.未经允许，你不能来这儿。have?to?的用法?1）must表示一种主观的需要，而have?to?表示一种客观的需要，意思是“不得不”。?如：?Ihavetoattendanimportantmeetingthisafternoon.Motherisout,soIhavetolookaftertheshop.2）have?to?的否定形式是don’thaveto,相当于needn’t。如：Theydon’thavetobuyacomputeratpresent.

【考例】Thebosshasgiveneveryoneaspecialholiday,sowe____gotoworktomorrow.(上海2007春)A.can’t B.mustn’tC.needn’t D.shouldn’t【点拨】考查情态动词。根据题意,可知这里表示“没有必要”,故只能选C项。3.must和needneed作情态动词时,只能用于疑问句和否定句。构成否定句和疑问句时不借助于助动词do。—NeedIfinishtheworktoday?—Yes,youmust./No,youneedn’t.1.Judgingfromhisaccent,hemustbefromthesouth,2.Itiseleveno’clockatnightandthelightsareoff.Theymustbesleepingnow,isn’the?aren