大学英语四级常用语法大学英语四级常用语法精选大学英语四级常用语法精选(17)might表示请求:MightIaskforaphotographofyourbaby?(比MayI…更客气一些)can't,couldn't表示否定的推测:Shecan'tbeserious.Amoresuitablebookcan'tbefound.(Itisnotpossibletofindamoresuitablebook.)Hecouldn't(can't)beoverfifty.should,oughtto:表示应该做的事,oughtto比should口气稍重一些.Youshould(oughtto)doashesays.Youshouldn't(oughtn'tto)talklikethat.但这两者间也有一些差别,在表示责任,义务等该做的事情时,常用oughtto,在表示某件事宜于做时,多用should,在下面的句子中这两个词就不宜换用:Youarehisfather.Yououghttotakecareofhim.Weshouldnotusetoomanybigwordsinoureverydayspeech.will,wouldshall,should表示意愿情态动词后接进行式,完成式和完成进行式:情态动词可以和动词的进行式构成谓语,表示”应该正在……”,“想必正在……”这类意思:Whyshouldwebesittingheredoingnothing?Thisisn'twhatIoughttobedoing.Shemightstillbethinkingaboutthequestionyouraised.Theymust(may)bewaitingforus,let’shurryup.Theycan'tbeusingtheroomnow.情态动词有时和动词的完成形式构成谓语,表示”应当已经……”,“想必已经……”这类意思:Ishouldhavethoughtofthat.Theyshouldn'thaveleftsosoon.Shemusthavearrivedbynow.Youneedn'thavetoldthemthat.Wherecan(could)hehavegone?Hecan'thavefinishedtheworksosoon.Hemaynothaveachievedallhisaims.Buthiseffortispraise-worthy.Weoughttohavegiveyoumorehelp.情态动词间或也可以和一个动词的完成进行式构成谓语,表示”应当一直在……”,“想必一直在……”这类意思:Theyaresweatingallover.Theymusthavebeenworkinginthefields.Theymayhavebeendiscussingtheproblemthismorning.Youshouldhavebeenwaitingforus.Whyhaven'tyou?Shecouldn'thavebeenswimmingallday.2016年大学英语四级语法指导(4)1.Thechildrenwenttheretowatchtheirontower_D_.AtoerectBbeerectedCerectingDbeingerectedwatch看电视用，看比赛用;see看电影用;感官动词watch，see，hear;感官动词+名词(代词)+dobeerected强调的是动作的结果;beingerected强调的是动作的过程。2.Theengine_D_smokeandsteam.AgivesupBgivesinCgivesawayDgivesoffgiveup放弃;givein屈服，让步;giveoff释放，放出(烟和气体);giveaway泄露，走漏风声;婚礼中新郎的父亲把新娘的手交给新郎的过程;赠送礼品。3.Themanagerpromisedtokeepme_C_ofhowourbusinesswasgoingon.AtobeinformedBoninformingCinformedDinformingkeepsb.+分词;informv.通知，告知;informsb.ofsth.通知某人某件事情keepmeinformed使我被告知。4.Thegoals_B_hehadfoughtallhislifenolongerseemedimportanttohim.AafterwhichBforwhichCwithwhichDatwhichfightwithsb.(注