情态动词是中学英语语法的重点,也是高考的热点。只用作情态动词的有:can/could,may/might,must,ought to,be able to;既可作情态动词又可作实义动词的有:need,dare;既可作情态动词又为助动词的有:shall/should/w1ll/would。 1情态动词need的用法 1. need作情态动词,一般用于疑问句和否定句中,表示“需要”、“必要”。当其用于现在时和将来时时,在宾语从句中可当过去时用。肯定回答用must(或have to, ought to, should) 来表达。否定式为need not / needn't表示“不必,不需要”。如: (1) You needn't show your passport at the entrance unless the guard asks you for it. (2) —Shall I tell Jack about it? —No, you needn't. I've told him already. 2. need作实义动词,意为“需要”、“要求”。如: (1) You don't need to leave so early. (2) He needs to try one more experiment. 2情态动词dare的用法 1. 情态动词,表示“敢”,后接动词原形,用于否定句、疑问句和条件状语从句中。如: (1) We dare not refuse their request. (2) Dare you walk through the forest at night? 2. 当实义动词用时,可用于各种句型中。dare作实义动词用在否定句和疑问句中时,其后接不定式有时可省去“to”。如: (1) Does he dare to come? (2) She dares to speak in front of big audience. (3) I have never dared(to) speak to him. 3can/be able to/could用法 1. can和be able to都表示“能力”。在英语语法中,can只有现在时和过去时,而be able to则有更多的形式。但当成功地完成某一具体动作时,通常不用could而用was / were able to来表示。这时was / were able to 相当于managed to, 表示“经过一番努力,终于能够完成某事”。如: (1) Can you use chopsticks? (2) The wounded man was able to get to the village and was saved in the end. 2. can和could都可以表示“能力、技能、许可、建议或请求和可能性”。但比较委婉客气地提出问题或陈述看法时,一般用could,回答时则用can。如: (1) Could you help me carry the bag? (2) Can I help you? 4may和might的用法 1. may和might均可表示“可能”,但may比might可能性大。如: —Why isn't he in class? He may be sick.(生病的可能性较大)[He might be sick.(生病的可能性较小)] 2. may和might均可表示“允许”,may用于现在时或将来时,might常用在间接引语中表过去时,但might也可用于现在时,表示比较委婉的语气,回答用may。如: (1) He says we may leave. (2) He said we might leave. 3. may和might均可表示“建议或请求”,但might比may 更客气,意思更肯定,没有过去时态的含义。 —May / Might I use your bike? Yes, you can / may. No, you mustn't. 5情态动词的基本用法 最近几年高考试题中常常借助语境来考查情态动词的基本用法及其区别,因此准确掌握情态动词的基本用法十分重要。 例1.Johnny,you___play with the knife,you __hurt yourself. A.won’t;can’t B.muStn’t:may C.shouldn't;must D.can’t:shouldn’ 【标准答案】B 【试题解析】mustn't表示“不可以;禁止”,分析题意可知第二个空表示某种可能性。 例2.-Will you stay for lunch? 一Sorry,___ My brother is coming to see me. A.I mustn‘t B.I can’t C.I needn’t D.1 won’t 【标准答案】B 【试题解析】分析题意可知因为“我弟弟要来看我”,所以“不能留下”,因此对别人的邀请或要求应给予礼貌的拒绝。A 项表示“禁止”;C项表示“不必要”;而D项表示“不会”,均不符合题意。故本题选B。 例3.The fire spread through the hotel very quickly but eVeryOne___get out. A.had to B.would C.could D. was able to 【标准答案】D 【试题解析】该题考查了could和be able to的区别,二者都可表示过去时间的能力,但如果表示过去成功地做了某事只能使用was/were able to do。 例4.-Shall I tell John about it? 一NO,you____. I've told him already. A.needn’t B.wouldn’t C.mustn’t D.shouldn't 【标准答案】A 【试题解析】情态动词shall在试题中表示征询对方意见或请求指示。后面的句子暗示“没有必要了”,故本题选A。 6情态动词表示推测 1.表示推测时,根据时间确定情态动词的结构做题时要分清情态动词与时间的关系,以便正确使用情态动词的结构,这也是高考的热门考点。 1)must表示推测,意为“一定??”,只能用于肯定句中。must have done意为“一定做过某事或某事肯定发生了” 例1:-Hi,Tom.Any idea where Jane is? - She 1n the classroom.I saw her there just now. A.shall be B.should have been C.must be D.might have been 【标准答案】C 【试题解析】由下文的I saw her there just now.可知她现在一定是呆在教室里。must用于肯定句中,表把握较大的推测。 例2:一The woman biologist stayed in Africa studying wild animals for 13 years before she returned. 一Oh,dear!Sne___a lot of difficulties! A.may go through B.might go through C.ought to have gone through D.must have gone through 【标准答案】D 【试题解析】由上文的stayed可知,此题是对过去情况的推测。根据上文studying wild animals for 13 years可以判断出她一定遇到了许多困难。 2)can,could表达推测时,一般用于疑问句和否定句中;could用于肯定句中,语气比may/might更弱。例如: 例1:-I ve taken someone else’S green sweater by mistake. 一It____Harryts.He always wears green. A.has to be B.w1]]be C.mustn’t be D.could be 【标准答案】D 【试题解析】后文说“他总是穿绿色衣服”,据此语境可推知,这件衣“可能是”哈利的,could表示可能性。 例2:-Do you know where David is? I couldn’t find him anywhere. 一Wel1.He____ have gone far.His coat’S still here. A.shouldn’t B.mustn’t C.can't D.wouldn't 【标准答案】C 【试题解析]can’t表示“不可能”。根据他的衣服还在这里可推测出他肯定没有走远。must也可以表示推测,但是mustn’t的意思是“禁止,不准”,推测否定的事情用can’t。3)may/might表达一种不太把握的推测,意为“或许,可能”;might的语气比may较婉转。 例如:Some people who don’t like to talk much are not necessarily shy;they ____just be quiet people. A.must B.may C.should D.would 【标准答案】B 【试题解析】不爱说话的人可能是安静的人,因此用may;must太确定了。 例如:-I can't find my purse anywhere. -you___ have lost it while shopping. A.may B.can C.should D.would 【标准答案】A 【试题解析】结合语境可知,回答者在提醒对方:或许购物时把钱包丢了。 2.情态动词表示推测时有一些特殊用法 1)should/ought to表示按常理推测将要发生什么 例如:-When can I come for the photos?I need them tomorrow afternoon. -They____be ready by 12 O0. A.can B.should C.might D.need 【标准答案JB 【试题解析】根据句意可推测出“照片应该是到l2点可以准备好”。 2)can也可用于肯定句中,表示一种理论上的可能性,在这种用法中can只能与动词原形连用。 例如:It is usually warm in my hometown in March,but it___be rather cold sometimes. A.must B.can C.should D.would 【标准答案】B 【试题解析】can用于肯定句中,表示“有时也会很冷”。 7情态动词表情感态度 高考题中除了考查上述所讲到的情态动词的基本用法以及表示猜测的用法之外,还考查了情态动词表示情感态度的其他用法。 1.Il有些情态动词+have done”结构还可以表示“批评”、“责备”、“惋惜”语气。主要有: 1)needn‘t+have done “本来不必 (但却做了某事)”。 例如:-Catherine,I have cleaned the room for you. -Thanks.You___1t.I could manage it myself A.needn’t do B.needn’t have done C.mustn’t do D.shouldn。t have done 【标准答案】B 2)could(不用can)+have done表示“本来能够(而事实上未做到)” 例如:He paid for a seat,when he entered free A.could B.would C.must D.need 【标准答案lA 【试题解析】句意为“虽然他本来能够免费入场,但他买了票”。 3)might+have done表示“本来可以做到??(而事实上未做到)” 例如: You might have worked out this problem,though it was a little difficult. 4)should/ought to+have done表示“本应该做某事(但没做)” 例如:-My cat is really fat. -You_____ have given her so much food. A.wouldn’t B.couldn’t C.shouldn’t D.mustn’t 【标准答案】C 2.shall用于第二、三人称,陈述句中,表示说话人给对方的命令、警告、允诺或威胁。 例如:-Excuse me,but 1 want to use yomr computer to type a report? -You____have my computer if you don’t take care of it? A.shah’t B.might not C.needn’t D.shouldn’t 【标准答案】A 【试题解析】本句可译为“如果你不对计算机爱护的话,你就不能使用我的计算机。” 3.must表示与说话人的愿望相反,意思是“偏要” 例如:John,look at the time.___you play the piano at such a late hour? A.Must B.Can C.May D.Need 【标准答案】A 4.should可以表示讲话人意外、惊奇、遗憾的感情色彩。 例如:You can’t imagine that a well—behaved gentlemen____be so rude to a lady. A.might B.need C.should D.would 【标准答案】c 【试题解析】此句意为“你想像不到一个穿着这么讲究的绅士竟然对一个女士如此无礼。”should可译为“竟然”。情态动词给人的感觉好像比较难,因为它的总类繁多,用法也比较多。但是如果考生认真审题,结合所给出的语境,正确把握说话者的语气、情感、态度,并且认真思考选项中情态动词的基本特征和用法,注意把握时间概念,情态动词也就迎刃而解了。
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