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Unit4Donteatinclass.,祈使句1.定义。用来表达命令、请求、劝告、警告、禁止等的句子叫作祈使句。祈使句通常省略主语you。例如:Bequiet,please.请安静。Pleasehaveaseat.请坐。2.句式结构。(1)Do型:动词原形+宾语+其他。例如:Gothisway,please.请这边走。(2)Be型:Be+表语+其他。例如:Beagoodkid!做个好孩子!,(3)Let型:Let+宾语+动词原形+其他。例如:Letmehelpyou.让我来帮你。注意:祈使句的否定形式一般是在动词原形前加dont构成,有时也可直接用no开头表示禁止。例如:Dontbelateforschool!上学不要迟到!Nosmoking!禁止吸烟!,haveto与must的用法haveto和must均可表示“必须”。must更加强调说话者的主观意愿;而haveto强调客观的必要性,意为“不得不”。两者的否定式含义大不相同。mustnt表示“不准;禁止”,而donthaveto表示“不必”。例如:Imustgonow,orIllbelate.我现在必须走了,不然我就会迟到了。Shehastohelphermotherlookafterhersister.她不得不帮着她妈妈照顾妹妹。Youmustntswimintheriver.你不准在河里游泳。Youdonthavetodoitnow.你现在不必做这件事。注意:以must开头的一般疑问句,其肯定回答用must,否定回答用neednt或donthaveto。例如:MustIfinishtheworknow?我现在必须完成这项工作吗?Yes,youmust./No,youdonthaveto.是的,你必须完成。/不,你不必现在完成。,.根据句意用所给词的适当形式填空1.Do(do)theworkrightnow,Jim.2.Pleasetell(tell)methenews.3.Letsplay(play)soccernow.4.Youmustcome(come)toschoolontime.5.Notalking(talk)here!.根据句意用must或haveto的适当形式填空1.Youmustdoityourself.2.MustIreadthebookinthereadingroom?No,youdonthaveto.3.Itslate.Jimhastogohome.4.MustLilykeepquiet?Yes,shemust.5.Youdonthavetogetupearlyonweekends.,.按要求完成句子,每空一词1.Youcantlistentomusicwhenyourmotherissleeping.(改为祈使句)Dontlistentomusicwhenyourmotherissleeping.2.Hehastobeinbedbytenoclock.(改为一般疑问句)Doeshehavetobeinbedbytenoclock?3.Youmustcomehereearlythisafternoon.(改为祈使句)Comehereearlythisafternoon.4.Letherhelpyou.(改为否定句)Dontletherhelpyou.5.Shehastorideherbiketogohome.(改为否定句)Shedoesnthavetorideherbiketogohome.,
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