ModalVerbs 情态动词有can(could),may(might),must(must),haveto,shall(should),will(would),need(need),dare(dared),oughtto 等。情态动词无人称和数的变化。它不能单独使用，必须跟其后的动词原形构成谓语。情态动词的具体用法如下：一、can,could1、表示能力。a. CanyouspeakEnglish?b. Canyoufinishthisworktonight?c. Mancannotlivewithoutair.Note:(1)can 表示能力时，可用 beableto代替。a. I'llnotbeabletocomethisafternoon.(2)当我们要表示“某件事情已经成功”时，应用 was/wereableto,不能用 coulda.Hesawwellandhewasabletoswimtotheriverwhenthefloodhappened.b.Hewasabletogotothepartyyesterdayeveningandheenjoyedhimselfverymuch.2、表示客观可能性a. Peoplewholivenearairportscanhavetheirhearingharmed.b. Theboycansometimesbeverynaughty.（表示某人或某物一时的情况，“有时会。。。”）c. Theinventioncanbeimproved.d. Evenexpertscanmakemistakes.e. Hecan'tbeinBeijingnowbecauseIsawhimamomentago.f. Hehadalotofworktodolastnight,sohecouldn'thavegonetoseeafilm.Note:在肯定句中用 can 表示可能性时，其含义是理论上的可能性，不表示实际的可能性，也就是说，不涉及到是否真会发生。3、表示惊异、怀疑、不相信的态度（主要用与否定句、疑问句或感叹句中）a. Canthisbetrue?b. Howcanyoubesocareless!c. Thiscannotbedonebyhim.4、表示请求和允许。a. ---CanIgonow?---Yes,youcan.b. Youcansmokeifyouwantto.c. Youcan'tpickflowersinthispark.Note:could 也可以表示请求，语气较委婉，主要用于疑问句，不用于肯定句，回答应用 can---CouldIcometoseeyoutomorrow?---Yes,youcan./No,I'mafraidnot.5、can 的一些其他惯用法(1).cannotbut,cannothelpbut,cannotchoosebut+动词原形，意思为“不得不，只得”。a.Icannothelpbuttellherthetruth.2.cannothelpdoingstha. Icannothelplaughing.3.cannot…too/enough,cannevertooa. Youcannotbetoocarefulwhenyoucrossthestreet.b. Icannotthankyoutoomuchforyourkindness;Iowemyprogresstoyou.二、may,might1、表示许可。a.Youmaygonow.b. Wemaykeepthebooksfortwoweeks.c. ---MayIsmokehere?---Yes,youmay./No,youmaynot./No,youmustn't.2、表示可能性a.Hemaybewaitingforyouatthestation.b. Theymayhavegotlost.Note:表示可能性时，may...
