情态动词表推测的用法表示推测的情态动词有must,can,could,may,might,should等。表示对现在或将来的推测：“情态动词+动词原形”表示对正在进行的动作的推测：“情态动词+bedoing”表示对过去的推测：“情态动词+havedone”一、must表示推测的用法must表示推测时，只用于肯定句，表示很大的可能性，意为“肯定会…一定…”。例如：1.Youhaven’teatenanythingsincethismorning;youmustbehungry.2.Themachinedoesn’twork.Theremustbesomethingwrong.3.Ididn’thearthephone.Imusthavebeenasleep.4.Thetemperaturemusthavedroppedtobelowzerolastnightbecausethewaterisfrozen.二、can/could表示推测时，可用于肯定句否定句和疑问句。1．用于肯定句中表推测时，指“有时候可能会”之意。例如：①Evenexperiencedteacherscanmakemistakes.②TheWorldWideWebissometimesjokinglycalledtheWorldWideWaitbecauseitcanbeveryslow.2.用于疑问句中表推测时，含有怀疑或疑问的意味。例如：①Someoneisknockingatthedoor.Whocanitbe?②Whydoesheknowthis?Cansomeonehavetoldhimaboutit?③Canthenewsbetrue3.can’t/couldn’t用于否定句中表推测是语气最强的否定推测，意为“不可能…;一定不…”。例如:①Thestorycan’tbetrue.②---IsthatAnn’shusband?---No,itcann’tbehim—I’msurehedoesn’twearglasses.③Youcann’thaveseenheratthepartyyesterday,becauseshewasinhospital.三、may/might表示推测的用法1.may/might表示推测时，用于肯定句，表示无把握的推测，意为“可能，或许”。例如：①Hemay/mightbewritingaletternow.②Theymayhavebeendiscussingtheproblemthismorning.③---Excuseme.IsthistherightwaytotheSummerPalace?---Sorry,I’mnotsure.Butitmaybe.2.maynot/mightnot表示推测时，用于否定句，表示(无把握的)否定推测，意为“可能/或许不”。例如：①Shemaynothaveheardofyoubefore.四、should表示推测的用法should表示推测时，表示按常规、常理的推测，即“(正常情况下)按理应该”例如：①It’snearlyseveno’clock.Jackshouldbehereatanymoment.②Threeweeksshouldbeenough.③Thereshouldn’tbeanydifficultyaboutpassingthedrivingtestsinceyouhavepracticedalotinthedrivingschool.注：表推测时might不是may的过去式，could不是can的过去式，所以might/could+v不表示对过去的推测,而是表示might/could比may/can推测的可能性小.五、情态动词+havedone表示“原本...而未...”的情态动词有could/might/should/oughtto/would等.1.couldhavedone表示本来能做某事而实际没有做Hecouldhavepassedtheexam,buthewastoocareless.2.mighthavedone表示本可能做某事而实际没有做Itwasreallydangerous。Imighthavekilledmyself.Imighthavecompletedtheworkearlier.3.shouldhavedone表示本应该做某事而实际没有做=oughttohavedoneTom,youaretoolazy.Theworkshouldhavebeenfinished.Yououghttohavebeenherefiveminutesago.4.wouldhavedone虚拟语气,表示对过去事实相反的假设Iwouldhavetoldyouallabouttheboy’sstory.Butyoudidn’taskme.Withoutyourhelp,Iwouldn’thavefinishedthework.
