[讲解]高中英语情态动词精讲与解析

[讲解]高中英语情态动词精讲与解析 高中英语情态动词精讲与解析 概 说 助动词(auxiliary)主要有两类:基本助动词(primary auxiliary)和情态助动词(modal auxiliary)。基本助动词有三个:do, have和be;情态助动词有十三个:may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to. 上述两类助动词的共同特征是，在协助主动词构成限定动词词组时，具有作用词的功能: 1) 构成否定式: He didn't go and neither did she. The meeting might not start until 5 o'clock. 2) 构成疑问式或附加疑问式: Must you leave right now? You have been learning French for 5 years, haven't you? 3) 构成修辞倒装: Nowhere can he obtain any information about his sister. Hardly had he arrived when she started complaining. 4) 代替限定动词词组: A: Who can solve this crossword puzzle? B: Tom can. A: Shall I write to him? B: Yes, do. 情态助动词的特征 基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想: What have you been doing since? (构成完成进行体，本身无词义) I am afraid I must be going. (一定要) You may have read some account of the matter. (或许已经) 除此之外，情态助动词还有如下词法和句法特征: 1) 除ought和used以外，其他情态动词后面只能接不带to的不定式。如果我们把ought to和used to看做是固定词组的话，那么，所有情态动词无一例外地只能接不带to的不定式: We used to grow beautiful roses. I asked if he would come and repair my television set. 2) 情态助动词在限定动词词组总总是位居第一: They need not have been punished so severely. 3) 情态助动词用于第三人称单数现在时的时候，没有词形变化，即其词尾无-s形式: She dare not say what she thinks. 4) 情态动词没有非限定形式，即没有不定式、-ing分词和-ed分词形式: Still, she needn't have run away. 5) 情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间: Would you mind very much if I ask you to do something? She told him he ought not to have done it. 6) 情态助动词之间是相互排斥的，即在一个限定动词词组中只能出现一个情态助动词，但有时却可以与have和be基本助动词连用: You should have washed the wound. Well, you shouldn't be reading a novel. 现将情态助动词的各种形式列表如下: 情态助动词的意义和用法 情态助动词从最普通的意义上来说，是修饰分句意义的一种方式，它可以反映说话者对其表述是否真实和可能的程度作出判断。但不同的情态助动词本身所包含的意义和用法又不同，下面逐个分析。 1) can和could的用法 1. 表示能力或客观可能性，还可以表示请求和允许。如: Can you finish this work tonight? Man cannot live without air. — Can I go now? — Yes, you can. 注意:?could也可表示请求，预期委婉，主要用于疑问句，不可用于肯定句，答语应用can(即could不能用于现在时态的简略答语中)。如: Could I come to see you tomorrow? Yes, you can. (否定答语可用No, I'm afraid not.) ?can表示能力时，还可用be able to代替。如: I'll not be able to come this afternoon. 2. 表示惊异、怀疑、不相信的态度。(主要用在否定句、疑问句或惊叹句中) Can this be true? How can you be so careless! This cannot be done by him. 3. “can(could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑或不肯定。如: He cannot have been to that town. Can he have got the book? 2) may和might的用法 1. 表示许可。 表示请求、允许时，might比many的语气更委婉一些，否定回答时要用mustn't表示“不可以”、“禁止”、“阻止”之意。如: You may drive the car. — Might I use your pen? — No, you mustn't. 用May I ... 征询对方许可在文体上比较正式，在口气上比较客气。在日常口语中，用Can I ... 征询对方意见在现代口语中更为常见。 2. 用于祈使句中表示祝愿。如: May you succeed! 3. 表示推测、可能(疑问句不能用于此意)。 He may be very busy now. 4. “may(might) + have + 过去分词”表示对过去发生的行为的推测。如: He may not have finished the work. 3) must和have to的用法 1. 表示必须、必要。如: You must come in time. 回答must引出的问句时，如果是否定的回答，不能用mustn't，而要用needn't或don't have to。 — Must we hand in our exercise books today? — Yes, you must. (No, you don’t have to.) 2. “must be + 表语”的结构表示推测，它的否定或疑问式用can代替must。 This must be your pen. 3. “must + have + 过去分词”的结构常用在肯定句中，表示对过去发生的行为的推测。它的否定或疑问式用can代替must。 He must have been to Shanghai. 4. have to的含义与must相似，两者往往可以互换使用，但have to有各种形式，随have的变化而定。must与have to有下列几点不同: ? must表示的是说话人的主观看法，而have to则往往强调客观需要。如: The play is not interesting. I really must go now. I had to work when I was your age. ? must一般只表现在，have则有更多的时态形式。 ? 二者的否定意义不大相同。如: You mustn't go. 你可不要去。 You don't have to go. 你不必去。 ? 询问对方的意愿时应用must。如: Must I clean all the room? 4) dare和need的用法 1. need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must, have to, ought to,或should代替。如: You needn’t come so early. — Need I finish the work today? — Yes, you must. 注意:needn't + 不定式的完成式“表示本来不必做某事而实际上做了某事”。如: You needn't have waited for me. 2. Dare作情态动词时，主要用于疑问句、否定句和条件从句中，一般不用在肯定句中。如: How dare you say I'm unfair. He daren't speak English before such a crowd, dare he? 3. Dare和need常用作实义动词，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如: I dare to swim across this river. He does not dare (to) answer. Don't you dare (to) touch it! I wondered he dare (to) say that. He needs to finish it this evening. 5) shall和should的用法 1. Shall用于第一人称，表示征求对方的意愿。如: What shall we do this evening? 2. Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如: Shall we begin our lesson? When shall he be able to leave the hospital? 3. Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如: You shall fail if you don't work harder. (警告) He shall have the book when I finish reading. (允诺) He shall be punished. (威胁) 4. Should表示劝告、建议、命令，其同义词是ought to;在疑问句中，通常用should代替ought to。如: You should go to class right away. Should I open the window? Should的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子: ? I should think it would be better to try it again. 我倒是认为最好再试一试。 ? You are mistaken, I should say. 依我看，你是搞错了。 ? I should advise you not to do that. 我倒是劝你别这样做。 ? This is something I should have liked to ask you. 这是我本来想问你的。 从以上例句可以看出:情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。 Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如: ? Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。 ? If you should change your mind, please let us know. 万一你改变主意，请通知我们。 ? Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。 此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如: ? Why should you be so late today? 你几天怎么来得这么晚, ? — Where is Betty living? — 贝蒂住在哪里, — How should I know? — 我怎么会知道呢, ? I don't know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。 5. “should + have + 过去分词”结构一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如: She should have finished it. I should have helped her, but I never could. You should have started earlier. 6) will和would的用法 1. 表示请求、建议等，would比will委婉客气。如: Would you pass me the book? 2. 表示意志、愿望和决心。如: I will never do that again. They asked if we would do that again. 3. 用“will be”和“will(would) + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如: This will be the book you want. He will have arrived by now. The guests would have arrived by that time. I thought you would have finished this by now. 4. Would可表示过去反复发生的动作或某中倾向。Would表过去习惯时比used to正式，并没有“现已无此习惯”的含义。如: The wound would not heal. During the vacation he would visit me every week. 5. 表料想或猜想。如: It would be about ten when he left home. What would she be doing there? I thought he would have told you all about it. 7) ought to的用法 1. Ought to表示应该。如: You ought to take care of him. 2. 表示推测。注意与must表示推测时的区别: He must be at home by now. (断定他已到家) He ought to be home by now. (不十分肯定) This is where the oil must be. (比较直率) This is where the oil ought to be. (比较含蓄) 3. “ought to + have + 过去分词”表示过去应做某事而实际未做。如: You ought to have asked him (but you didn't). 这时，ought to和should可以互相换用。 注意:在美国英语中，ought to用于否定句和疑问句时，to可以省略。如: Ought you smoke so much? You oughtn't smoke so much. 8) used to，had better，would rather的用法 1. Used to表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变。 如: He told us he used to play football when he was young. 在疑问句、否定句、否定疑问句或强调句中，可有两种形式: 疑问句 Did you use to go to the same school as your brother? Used you to go to the same school as your brother? 否定句 I usedn't to go there. I didn't use to go there. Usedn't 亦可拼作usen't，但发音皆为[ju:znt]。 否定疑问句 Usen't you to be interested in the theatre? Didn't you use to be interested in the theatre? 强调句 I certainly used to smoke, but it was a long time ago. I certainly did use to smoke, but it was a long time ago. 其反意疑问句或简略回答中，也有两种形式: She used to be very fat, didn't she? (正式)/ use(d)n't she? (口语) Did you use to play chess? Yes, I did. Used you to get up early in the morning? Yes, I did. (Yes, I used to.) 2. Had better意为“最好”，后接不带to的不定式。如: — We had better go now. — Yes, we had (we'd better / we had better). Hadn't we better stop now? (Had we better not stop now?) I think I'd better be going. (用于进行时态，表“最好立即”) You had better have done that. (用于完成时态，表未完成动作) 注:?had best与had better同意，但较少用。?You had better … 用于同辈或小辈，对 长辈不可用。 3. Would rather意为“宁愿”，表选择，后接不带to的不定式。如: I'd rather not say anything. Would you rather work on a farm? — Wouldn't you rather stay here? — No, I would not. I'd rather go there. 由于would rather表选择，因而后可接than。如: I would rather work on a farm than in a factory. I would rather watch TV than go to see the film. I would rather lose a dozen cherry trees than that you should tell me one lie. I'd rather you didn't talk about this to anyone. (句中的'd rather不是情态动词，would在此是表愿望的实义动词) 高中情态动词的重难点突破 一.概念: 情态动词是表示能力,义务,必须,猜测等说话人的语气或情态的动词. 二.相关知识点精讲: 1(can 1)表能力 can表能力时意味着凭体力或脑力或技术等可以无甚阻力地去做某事。 I can climb this pole. 我能爬这根杆子。 He is only four , but he can read. 他只有4岁，但已认得字了。 Fire can’t destroy gold. 火烧不毁金子。 因为can不能和其他助动词连用，所以表示将来式时用will be able to You will be able to skate after you have practiced it two or three times. 你练习两三次后就会溜冰了。 2)表可能性 多用于否定与疑问结构中，但也可用在肯定句中。 Can the news be true? 这消息可能是真的吗, It can’t be true. 它不可能是真的。 What can he possibly mean? 他可能是什么意思, can 用在肯定句中表示理论上的可能性(一时的可能)。 A horse in the center of London can cost a lot of money. Attending the ball can be very exciting. The road can be blocked. 这条路可能会不通的。 may 在肯定句中表示现实的可能性。 The road may be blocked. 这条路可能不通了。 3)表示允许(和may意思相近)常见于口语。 Can (May) I come in ? 我能进来吗, Can I smoke here ? 我可以在这里抽烟吗, 2.could的用法 1)表过去的可能和许可，(多用于间接引语中) At that time we thought the story could not be true. 那时我们认为所说的事不可能是真的。 Father said I could swim in the river. 爸爸说我可以在河里游泳。 2)表过去的能力 I could swim when I was only six. 我刚六岁就能游泳。 Could在肯定句中表示过去的能力时，常表抽象的一般的能力。 He could be very naughty when he was a child. 他小时候会是很顽皮的。 允许”。可表示委婉客气的提出问题或陈述看法 3)表“ Could I use your bike? Yes, you can. 他会记得那时吗? I’m afraid I couldn’t give you an answer today. 恐怕我今天不能回答你。 The teacher said you could go to the store for sweets. 老师说你可以去商店买糖。 4)Could/can+have done 结构表示对过去发生的事情的“怀疑”或“不肯定”。 could 加完成式还用于肯定句时一般表过去可能完成而却未完成的动作。 Can they have won the basketball match, 他们赢了那场篮球赛吗, What you referred to just now can have made her very sad. 你刚刚所谈到的可能令他很伤心。 You could have completed the task a little earlier. 你本来能早点完成任务的。(但事实上并没有提前完成任务) I could have passed my examination easily but I made too many stupid mistakes. 我本可以轻易通过考试，但我犯了太多不该犯的错误。 如表具体做某一件事的能力时，则须用 be able to . He was able to translate the article without a dictionary. 他可以不用词典翻译那篇文章。 Can表示一贯的能力 ，be able to表示客观能力和通过努力可以达到的能力 I can’t swim. But I am sure I will be able to swim through more practicing. The fire spread through the hotel, but everyone was able to get out When the boat sank he was able to swim to the bank 3.may 的用法 1)表示请求、可以、允许。 You may drive the tractor. 你可以开那台拖拉机。 2)当回答由may 引起的问题时，否定答语要用must not,表示“不许可”、“不应该”、“不行”。 May I come in? Yes, you may. No,you can’t No, you may not . No ,you mustn’t No ,you’d better not. 3) may /might 推测性用法 可能 He may be right. He may not come today (可能不) He may /might come tomorrow. 注意 : (1)只用于肯定和否定句中,不用于疑问句中。 (2) might 比may可能性更小 He might get a job. He may get a job. (3) may no 可能不 can not不可能 He may not come He can’t come 3)表建议(可和as well 连用) You may(might)as well stay where you are. 你还是原地待着好。(may as well 有“还是„„的好”的含义) 4)表祝愿 May you be happy! might 1)表过去的“可能”和“允许”多用于间接引语。 She said that he might take her dictionary. 她说他可以拿她的词典去用。 除在间接引语中外，might一般不表示过去的“可能”与“许可”。表过去的“可能”可用could，表过去的“许可”可用were (was) allowed to。 2)表现在的“可能”，其可能性要比may小。 Electric irons could be dangerous; they might give you a severe shock. 电熨斗会有危险，它可能电着人。 3)may (might) + have +done 表示对过去发生行为的推测，含有“想必”、“也许是”的意思。 It may have been true. 这事也许是真的。 He might not have settled the question. 他可能尚未解决那个问题。 4.must 的主要用法。 1)表示必须、必要 We must do everything step by step .我们必须按部就班地做一切事情。 Why must you always bother me? 为什么你偏要打扰我呢。 2)must be + 表语的结构，通常表示猜测，含有“一定”之意。(只用在肯定句中) He must be an honest boy. 他一定是个诚实的男孩。 This must be your room. 这一定是你的房间。 3)must 的否定式有两个:当回答由must引起的问题时，否定答复要用needn’t或don’t have to 表示“不必”、“无须”、“用不着”、“不一定”的意义。当表示“不应该”、“不许可”、“禁止”时，就用must not。 Must I go tomorrow?明天我必须去吗, Yes, please.是的，请吧～ No , you needn’t. 不，你不必去。 4)must +have +过去分词的结构，常用在肯定句中，表示对过去发生行为的推测，含有“一定”、“准是”的意思。否定和疑问句用can。 She must have studied English before.她以前一定学过英语。 5.have to的含义与must是很接近的,只是have to 比较强调客观需要，must着重说明主观看法。 I must clean the room.(主观想法) I have to clean the room.(客观需要) 另外，have to 能用于更多时态: We had to be there at ten .我们得在十点钟到那里。 We will have to reconsider the whole thing. 这一切我们将不得不重新加以考虑。 have to 的否定式:don’t have to do 表示“不必做„„”之意。 6.ought to 的用法 Ought to 后接动词原形，表义务，但不及must 那样具有信心，如: You don’t look well. You ought to go to see the doctor. 你气色不好，应该去看病。 Ought to 用于否定句，其否定形式可缩略为oughtn’t ，如: You oughtn’t to smoke so much. 你不应该抽这么多烟。 也可以用于疑问句，如: Ought you to smoke so much?你应该抽这样多烟吗, Ought to 在间接引语中表过去时形式不变，如: He said you ought to tell the police. 他说你应该去报告警察。 7.shall的用法 1)用于第一人称征求对方的意见，如: What shall I wear on the journey? 我路上穿什么好呢, Shall we dance? 我们跳舞好吗, 2)shall 用于第二、三人称时表允诺，警告，命令，威胁(现已少见)，如: She shall get her share. 她可以得到她的一份。 You shall have it back tomorrow.你明天可以将它拿回。 情态动词should一般不应被认为是情态动词shall的过去式，主要用法有: 1)用于第一人称疑问句中询问对方的意愿，但语气较委婉温和，如: What should we do now? 我们现在该怎么办, 2)表示应该、必须，常与must 换用。例如: We should (must) master a foreign language at least. 我们应当至少掌握一门外语。 3)“should+be+表语”的结构，表示推测或惊奇。例如: They should be back by now. 他们现在应该回来了吧。 I am sorry that she should be so careless. 我感到遗憾她竟会那样粗心。 4)“should+have+过去分词”的结构，表示过去该做而实际上尚未做的动作或行为;其否定则表示发生了不应该发生的行为。其同义结构“ought to have +过 去分词”,表示过去“早应该”、“本当”之意，语气较强。例如: I should have thought of that. 这一点我是应当想到的。(但没想到) They should not have left so soon.他们不应当走得这么早。(但已走了) 5) 在“It is natural (strange, natural, necessary, surprised, impossible, important ) that„„”句型中，主语从句中的谓语动词要用should +动词原 形”表示“理所当然”、“奇怪”、“必要”、“惊异”等的意思。在lest(以 免)、for fear (that) (以防)、in case(以备万一)等之后也要用should+ 动词原形;在advise, sugest, order, demand, request 等的从句中 should+do”例如: It is necessary that he(should) be sent there at once. 有必要马上派他到那里去。 It is strange that he should say so. 他会说这样的话真是奇怪。 Let us go at once lest we should be late for the train. 我们马上走吧，以免赶不上火车。 8..will和would的用法 1)表示意志，决心或愿望。例如: Surely we will support all the people in the world in their struggle for peace. 我们一定要支持全世界人民争取和平的斗争。 He would not let me try it . 他不肯让我去试。 2)will表示经常性、习惯性、倾向性，would表示过去的习惯行为。 He will sit there hour after hour looking at the traffic go by. 他会经常一连几个小时坐在那儿观看来往的车辆。 He would come to see me when he was in Beijing. 他在北京时，常来看望我。 3)用于第二人称作主语的疑问句中，表示对对方的请求，would的语气比will委碗 Would/will you kindly tell me the way to the station? 请问到火车站怎么走, 4)表可能性 This will be the book you are looking for. 这可能就是你要找的书。 She eould be about 60 when she died. 他死时大概60岁。 9. need和dare的用法 情态动词need 实义动词 need 现 You need (not) do You (don’t) need to do 在 时 He need (not) do He needs (doesn’t need) to do 过 You needed (didn’t need) to do 去 时 He needed (didn’t need) to do 将 You need (not) do You will (not) need to do 来 时 He need (not) do He will (not) need to do 句型 时态 动词 情态动词dare 实义动词 dare 肯定句 现在时 dare to 少用 dare/dares to do 过去时 dare to 少用 dared to do 否定句 现在时 daren’t/dare not do do/does not dare (to) do 过去时 dared not do did not dare (to) do 疑问句 现在时 Dare he do? Do you/Does he dear (to) do? 过去时 Dared he do? Did he dare (to) do needn’t have v-ed 表示过去做了某事，但没有做的必要，意为“本没必要„”。 例如: You needn’t have waken me up; I don’t have to go to work today 10.表推测的情态动词句子的反意疑问句 He must/may be in the room, isn’t he? He can’t be in the room, is he, He must have finished the work, hasn’t he? He may have done the work last night, didn’t he? :情态动词+行为动词进行式 情态动词+行为动词进行式(即情态动词+ be + v-ing形式)，表示推测或 评论某动作现在是否正在进行。例如: 1)He must be playing basketball in the room. 2)She may be staying at home. 11.情态动词+行为动词完成进行式 情态动词+行为动词完成进行式(即情态动词+ have been + v-ing 形式)， 表示推测或评论过去某动作是否正在进行或一直在进行。例如: 1)They should have been meeting to discuss the problem. 2)He may / might have been buying stamps in the post office when you saw him. 12.used to +v, be used to +v-ing和be used to +v (1)used to +v意为“过去常常”，“过去一直”;be used to +v-ing / n(名词)意为“习惯于”;be used to +v意为“被用来(做某事)”。 (2)used to只表示过去，而be used to +v-ing / n可表示现在、过去或 将来。例如: 1)He used to smoke. Now he doesn’t. 2)He’s quite used to hard work / working hard. 3)The knife is used to cut bread. 13(用作情态动词的其他短语 would rather, would sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well等可用作情态动词。 例如: 1)The soldier would sooner die than surrender. 2)The brave soldier would as soon die as yield to such an enemy. 3)I’d rather walk than take a bus. 4)If you don’t like to swim, you may just as well stay at home. 注:这些短语后一般直接跟动词原形.would (had) rather, would (had) sooner, would (just) as soon后可跟that 引导的从句，that 常省去，从句 要用虚拟语气。对现在和将来的假设用过去时，对过去的假设用过去完成时。例 如: 1)I would rather you came on Sunday. 2)I would sooner you hadn’t asked me to speak yesterday. 三. 巩固练习: 1. _____ you ready? (A) Are (B) Have (C) Will (D) Can 2. ____ here early? (A) Will he (B) Was he (C) Did he be (D) Were he 3. I ___ happy about the price of eggs. (A) am't (B) am not (C) do not (D) won’t 4. Since last year I____ him only once. (A) have seen (B) have been seeing (C) see (D) was seeing 5. Donald ___ sixteen tomorrow. (A) is being (B) going to be (C) shall be (D) will be 6. I ___ the story at all. (A) don't like (B) like (C) am fond of (D) would like 7. I would rather ___ than play now. (A) to study (B)am studying (C) study (D) studied 8. I'd rather you ___ anything about it for the time being. (A) do (B) didn't do (C) don't (D) didn't 9. The car___much money. (A) not cost (B) not have cost (C) isn't cost (D) didn't cost 10. I ___ like to eat fish. (A) am (B) have (C) do (D) be 11. ___ repeat the question? (A) Shall I (B) Will I (C)Would you like that I (D) Do you want that I 12. My teacher knows more than ___. (A) my uncle knows (B) my uncle does (C) they know (D)they don't know 13. He___to meet us at the station, but didn't see us. (A) did go (B) did went (C) goes (D) had 14. Not only ____us light. (A) does the sun give (B) the sun gives (C) gives the sun (D) the sun does give 15. ____ you tell me what has happened? (A) May (B) Must (C) Can (D) Could 16. Anne___tomorrow. (A) can sing (B) can to sing (C) is going sing (D) going to sing 17. You___hand it in at once, you may hand it in tomorrow. (A) needn't (B) may not (C) can't (D) must not 18. Tell the boy that he ___ in the river. (A) swims (B) swim (C) swimming (D) to swim 19. Joan___play on Saturday. (A) going to (B) can (C) is going (D) can to 20. Susan and I can go to the lecture ___. (A) but neither can Charles (B) and so Charies can (C) but Charles can't (D) and Charles also can 四.答案 1. (A) 2, (B) 3. (B) 4. (A) 5, (D) 6, (A) 7. (C) 8. (B) 9. (9) 10, (C) 11. (A) 12. (B) 13. (A) 14. (A) 15. (D) 16. (A) 17. (A) 18. (B) 19. (B) 20, (C)