2023年（七升八）新八年级暑假衔接自学课（人教版）02 情态动词can,must,have to的用法X#K一、情态动词的基本用法情态动词是表示说话人的语气、情态等的一类词。如：can(能，会)、may(可以)，以后我们还将学到must(必须)、should(应该)、would(应该、想要)等。情态动词在运用时有以下三方面的特征：1. 情态动词无主语人称及单复数的变化。They can play the piano.She can speak a little English.You may watch TV after supper.2. 情态动词在句中运用时，后接动词原形。The girl can sing English songs.I can play Chinese chess.3. 含情态动词的肯定句变为一般疑问句时，将情态动词提至句首，后加?；变否定句时，在情态动词后加上not即可。This boy can dance well.Can this boy dance well? (一般疑问句) Yes, he can. / No, he cant.This boy cant dance well. (否定句)二、情态动词can的用法小结can是情态动词，意为能；会，表示某人或某物具备的能力，还可用来提出请求，没有人称和数的变化，后面直接接动词原形。下面来看一下它的具体用法。1. 表示有能力做某事，意为能；会。I can speak English.我会讲英语。He can play basketball.他会打篮球。来【典例】I hear you have a home robot.Yes, its amazing. It _ do all my housework.A. must B. should C. could D. can【答案】D【解析】我听说你有一个家用机器人。是的，它真令人惊奇。它能做我的所有家务活。Must2. 表示许可，意为可以。You can sit here.你可以坐在这儿。【典例】Can you please have a walk with me?Sorry, I _. I have something important to do now.A. mustnt B. neednt C. cant D. may not【答案】C【解析】Could/Can you.？是一个表示请求对方许可的句型，意为你可以吗？，肯定回答用Sure./Yes, I can.，否定回答通常用Sorry, I cant.。3. 情态动词can表示推测，意为可能，常用语否定句、疑问句中。It cant be a cat. It has a short tail. 它不可能是猫，它有一个短尾巴。【典例】Is that girl under the tree Mary?No, it _ be Mary. She is in Beijing now. A. cant B. neednt C. wouldnt D. shouldnt【答案】A【解析】本题用语境判断法。由答语第二句她现在在北京可知，树下的那个女孩不可能是玛丽。表示否定的推测，应用cant。下面一起来看一下can的句型变换：(1)变为否定句变为否定句时在情态动词can后加not，缩写为cant。She cant play the piano. 她不会弹钢琴。(2)变为一般疑问句变为一般疑问句时直接将情态动词can提到句首。肯定回答为：Yes, 主语can.否定回答为：No, 主语cant.Can you speak Japanese? 你会讲日语吗？Yes, I can./No, I cant.是的，我会。/不，我不会。【注意】用Certainly.作肯定回答，语气更肯定；用Sorry.作否定回答，语气则更委婉、客气。Can you sing? 你会唱歌吗？Certainly, I can.我当然会。Sorry, I cant.很抱歉，我不会。(3)变为特殊疑问句变为特殊疑问句时，其句型通常为疑问词can主语动词原形？What can you do? 你会做什么？含情态动词can的句子的句式变换否定句/一般疑问句及回答方式否定句主语cannot动词原形其他. 一般疑问句 Can主语动词原形其他？肯定回答 Yes，主语can. 否定回答No，主语cant.含情态动词can的特殊疑问句结构：特殊疑问词can主语动词原形其他？What can you read? 你能读什么？提问名词(词组)、代词特殊疑问词一般疑问句画线部分(要提问的部分)? 提问动词(词组)特殊疑问词一般疑问句画线部分(要提问的部分)do？(即用do替代画线部分) 【典例】1.Mom, can I play tennis?_ right now. Id like you to help me with the housework. A. No, you can B. Yes, you cant C. Yes, you can D. No, you cant【答案】D【解析】根据答语后一句可知现在不能去打网球，故回答为否定的，排除B、C，又因为A选项前后矛盾，故选D。2. She can draw a picture. (对画线部分进行提问)_can she _?【答案】What; draw【注意】情态动词can没有数和人称的变化，其后总跟动词原形She can do it well.她能做好它。情态动词can，可以表示能力，意为会，能。I can swim and skate.我会游泳和滑冰。2. must的用法（1）must表示主观义务，意思是应该，必须，其否定式mustnt意为不应该，不准。We must get there before five oclock. 我们必须在五点钟前赶到那儿。You mustnt break the rules. 你不要破坏规定。对用must所提问题的否定回答，常用neednt或dont have to，意思为：不必。Must I stay here after school? 放学后我还得留在这儿吗？No, you neednt / dont have to. 不了，没有必要。（2）must表示推测，意思为：一定，必定(只用于肯定句中)。He must be our headmaster. 他肯定是我们的校长。He must have seen the film last night. 他昨天晚上肯定看了那场电影。3. have to表示客观要求，意思为：不得不；必须；除此之外，别无选择。使用have to应注意以下几点：（1）have to后接动词原形，意为必须做；不得不做。We have no food home, you have to go and get some, Tom. 家里没有食物了，汤姆你得去买一些来。（2）have to 有人称、数和时态的变化，其第三人称单数形式为has to。She has to help her mom make dinner. 她不得不帮她妈妈做晚饭。Theres no bus here, so we had to walk home. 现在这里没有汽车了，我们只好走路回家了。（3）含有have to, has to的句子需分别借助动词do, does构成疑问句或否定句。Do they have to go now? 他们得现在回家吗？You dont have to go if you dont want to. 如果你不想去，你就不必去。【辨析】have to可以用于多种时态；而must只用于一般现在时或一般将来时。The composition is due to hand in this morning, so I had to finish it last night. 作文今天早晨到期，因此我不得不昨天晚上完成。【典例】Lingling, can I use your e-dictionary?Sure. But you _ return it after class.A. must B. can C. may D. would【答案】A一、单项选择1Everyone _ succeed if they have a chance.AshouldBcanChave to2_ I stay at home now?No, you neednt. ACanBMayCMustDNeed3_ I hand in the report today?No, you neednt.ACanBMustCShallDCould4I want to play outside, but I _ stay at home to do the housework. AcanBmayChave toDmust5 Could I take the picture book home, Mrs Rice? No, you _.You _ only read it here.Acant; canBcouldnt; canCcant; cantDcouldnt; may6She _ be Mary, but Im not sure.AmustBmayCcantDmustnt7Must I finish all the work at school?No, you _. You can do it at home.AmustntBhavent toCcantDdont have to8 What do you learn from Mr. Greens speech today? Tell me and Ill forget. Show me and I _ not remember. Let me try and Ill understand.AmustBcouldCneedDmay9Mom, can I play computer games? Yes, but you _ finish your homework first.AmustBcanCmayDneednt10_