八年级英语上册 Unit 2 Keeping Healthy Topic 2 I must ask him to give up smoking Section C情态动词can、may、must、need解析区别练习课件 （新版）仁爱版.ppt

unit2keepinghealthytopic2imustaskhimtogiveupsmokingsectionc 情态动词can may must need解析区别练习 情态动词 情态动词后面 动词原形 情态动词没有人称和数的变化 1 can icannotplaybasketball ineedbuyacomputer 2 能 need 需要 shecanrideahorse amyneedbuyabook 3 否定式构成是在情态动词后面加 not icanplaybasketball can 能 用法 表示能力 hecanspeakalittleenglish canyoufly 表示请求或允许 canihelpyou 表示猜测 thatcannotbeourenglishteacher becauseshehasgonetoshanghai could也可表示请求 语气委婉 主要用于疑问句 不可用于肯定句 答语应用can couldicometoseeyoutomorrow yes youcan 否定答语可用no i mafraidnot 注意 用法 表示请求或允许 mayigohome please 1 以may 表许可或请求 开头的一般疑问句 肯定回答用may 否定回答用mustn t或can t 2 在疑问句中不用于第二人称 表示可能性 用在肯定句 youmayberight no you may 可以 yes youmay 注意 might为may的过去式 但也可以代替may 语气较为婉转客气或更加不肯定 youmightberight might mustn t youcan t 试比较 youmaynotsmokehere 可能不 语气轻 youcan tsmokehere 不能 重 youmustn tsmokehere 决不可 最重 can t maynot mustn t 用法 既可以做情态动词 也可以做实意动词 实意动词 needtodosth 情态动词 needdosth ineedbuyabighouse need 需要 heneeddrivemehome doineedtobuyabighouse heneedstobuyabighouse needibuyabighouse yes youmust no youneedn t don thaveto 不必要 yes youdo no youdon t 用法 表示推测 肯定 一定 表示义务 必要或命令 youmustcomeearlytomorrow mustifinishmyhomeworkfirst theymustbeathome thelightison yes youmust no youdon thaveto needn t must 必须 注意 must开头的疑问句 其否定回答通常用don thaveto或needn t 而不用mustn t mustn t 禁止 否定时表示 禁止 youmustn tsmokehere 用法 it seleveno clock ihavetogonow itwasgettingdark hehadtofinishtheworkfirst idon thavetogonow hedoesn thavetofinishtheworkfirst haveto 必须 注意 haveto表示客观因素weareverygladattheparty butit s11 sowehavetoleavenow must表示主观因素wemuststudyhardtofindagoodjobforourselves must 必须 haveto must区别 mybrotherwasveryill soicallthedoctorinthemiddleofthenight hesaidthattheyworkhard youdon thavetotellhimaboutit youmustn ttellhimaboutit 你不一定要把此事告诉他 你一定不要把这件事告诉他 haveto must hadto must 区别 cani yes youcan no youcan t mayi yes youmay no youcan t mustn t needi yes youmust no youneedn t doineedto yes youdo no youdon t musti yes youmust no youneedn t 找伙伴 should应该shouldn t不应该youshouldfinishyourhomeworkontimeyoushouldn tgotobedtoolate exercises 1 mustwecleanthehousenow no you needn tb maynotc mustn td can t2 youreturnthebooknow youcankeepitnextweekifyoulike a can tb mustn tc needn td maynot3 johnny youplaywiththeknife youhurtyourself a won t can tb mustn t mayc shouldn t mustd can t shouldn t4 igobackbeforelunch no idon tthinkyou a need mustb do needtoc must havetod may oughtto a c b c 5 theteacher doalltheexercises butapupil a needn t mustb maynot mustc needn t needn td can t must6 mustifinishthisnovelthismorning no you a mustn tb mightnotc don thavetod can t7 thetaxi onlyholdsixpassengers itisfull you takethenextone a may mayb can mayc may