Unit4语法讲解及习题_情态动词must_may_can（表推测与意愿） -2025-2026学年外研版英语八年级下册

外研英语八下Unit4语法讲解及习题 情态动词must/may/can 表推测与意愿 一、语法概念讲解 1. 核心功能 情态动词must/may/can在本单元中主要用于表达对事情的推测 可能性 和帮助他人的意愿/责任，是日常交际中传递态度、提出帮助的核心语法点。 2. 具体用法细分 1 表“推测” 情态动词 可能性强度 用法场景 句式 例句 must 90% 极有可能，肯定推测 基于事实、逻辑或明显证据得出的结论 仅用于肯定句 ① 箱子很重，他肯定需要帮助。 The box is heavy. He must need help. ② 你看起来很累，肯定熬夜工作了。 You look tired. You must have worked late. may 50% 可能，不确定推测 没有明确证据，仅表达合理猜测 可与might互换，might可能性稍弱 肯定句/否定句 may not表“可能不” ① 天阴了，之后可能下雨。 It’s cloudy. It may rain later. ② 她可能不来派对，她很忙。 She may not come to the party—she’s busy. can 0% 不可能，否定推测 基于事实否定某事的可能性，语气坚决 仅用于否定句 can’t=不可能 ① 他不可能在家，门是锁着的。 He can’t be at home—his door is locked. ② 这个故事不可能是真的，太奇怪了。 The story can’t be true—it’s too strange. 2 表“帮助的意愿/责任” 交际场景高频用法 情态动词 核心含义 用法场景 例句 中文+英文 must “必须” 强调责任、义务 表达帮助他人是应尽的责任，语气强烈 我们必须帮老人过马路。 We must help the old man cross the road. may “可以” 委婉请求/主动提供帮助 主动提出帮助或请求许可时，语气礼貌委婉 我可以帮你拎包吗？ May I carry the bag for you? can “能够/可以” 表能力/意愿 表达自己有能力提供帮助，或主动提出帮忙，语气自然直接 我可以帮你写作业。 I can help you with your homework. 3. 易混点辨析 避免错误核心 ① can表推测时不能用于肯定句 √：He may be late. ×：He can be late. ； ② may not表“可能不”，而非“禁止” 禁止用mustn’t ； ③ must表推测时无过去式，描述过去的推测用“must have + 过去分词” He must have missed the bus. 他肯定错过了公交车。 ； ④ 表主动帮助时，can更口语化，may更礼貌 日常交流中can更常用 。 二、习题 题型1：用must/may/can can’t 填空 1. You look pale. You ___________ be ill. 2. The bus is late. It ___________ be stuck in traffic. 3. He ___________ be in the library—he told me he’d stay home. 4. We ___________ help the lost child find his parents. 5. ___________ I borrow your pen? I need to write down the address. 6. The cake is gone. Someone ___________ have eaten it. 7. It’s snowing heavily. We ___________ not go out tonight. 8. She ___________ know the answer—she’s good at math. 9. They ___________ finish the work today; the deadline is tomorrow. 10. ___________ you pass me the water bottle? I’m thirsty. 题型2：单项选择 1. —Is that Lucy? —It ___________ be her. She’s in London now. A. must B. may C. can’t 2. We ___________ help people in need—it’s the right thing to do. A. must B. may C. can 3. The cat ___________ be hiding under the bed—I heard a noise there. A. must B. may C. can’t 4. —___________ I use your phone? —Sure, here you are. A. Must B. May C. Can’t 5. He ___________ not like the gift—I don’t know his hobbies. A. must B. may C. can 6. You ___________ not lie to your friends—it hurts their feelings. A. must B. may C. can 7. The movie ___________ be interesting—many people are talking about it. A. must B. may C. can’t 8. I ___________ help you move the desk—I’m strong enough. A. must B. may C. can 9. —Where is Tom? —He ___________ be in the classroom. I saw him go there just now. A. must B. may C. can’t 10. It ___________ be raining outside—the ground is dry. A. must B. may C. can’t 题型3：根据场景补全对话 场景1：看到同学搬重物 A: Look! He’s carrying so many books. It ___________ be heavy for him. B: Let’s go and help. We ___________ carry some for him. 场景2：看到路人找不到路 A: That woman looks lost. She ___________ need directions. B: We ___________ go and ask if she needs help. 场景3：朋友感冒没来上课 A: Is Tom absent today? B: He ___________ have a cold—he was coughing yesterday. A: We ___________ share our notes with him after class. 题型4：改写句子 1. It’s possible that she will come to the party. 用may改写 She ___________ ___________ to the party. 2. I’m sure he is tired after running. 用must改写 He ___________ ___________ tired after running. 3. It’s impossible for him to finish the task alone. 用can’t改写 He ___________ ___________ the task alone. 4. We have a duty to help the poor. 用must改写 We ___________ ___________ the poor. 5. Is it okay if I use your umbrella? 用may改写 ___________ I ___________ your umbrella? 6. I am able to help you with the project. 用can改写 I ___________ ___________ you with the project. 7. I’m certain that the dog is hungry—it’s barking. 用must改写 The dog ___________ ___________ hungry—it’s barking. 三、答案及解析 题型1答案 1. must 解析：脸色苍白是明显证据，表肯定推测 2. may 解析：公交车晚点无明确原因，表不确定推测 3. can’t 解析：已告知待在家，否定“在图书馆”的可能性 4. must 解析：帮助迷路孩子是责任，用must表义务 5. May 解析：委婉请求借笔，用may更礼貌 6. must 解析：蛋糕消失，肯定被人吃了，表过去的推测 7. may 解析：雪大，推测“可能不外出”，表不确定 8. may 解析：擅长数学但无明确证据，表可能 9. needn’t 解析：截止日期在明天，不必今天完成，补充常见否定形式 10. Can 解析：请求递水瓶，口语化主动帮助，用can 题型2答案 1. C 解析：Lucy在伦敦，所以“不可能”是她，can’t表否定推测 2. A 解析：帮助有需要的人是正确的事，表责任义务，用must 3. A 解析：听到床底有声音，有明确证据，表肯定推测，用must 4. B 解析：请求使用他人手机，委婉礼貌，用may 5. B 解析：不知道对方爱好，所以“可能不”喜欢礼物，may not表不确定否定 6. A 解析：撒谎伤害朋友，表“必须不能”，用must not 7. A 解析：很多人讨论，有间接证据，表肯定推测，用must 8. C 解析：强调自己“有能力”帮忙搬桌子，用can表能力 9. A 解析：刚看到Tom去教室，有明确证据，表肯定推测，用must 10. C 解析：地面是干的，否定“在下雨”的可能性，用can’t 题型3答案 1. must; can 解析：搬很多书→肯定很重，用must；自己有能力帮忙，用can 2. may; can 解析：看起来迷路→可能需要方向，用may；主动提出帮忙，用can 3. must; can 解析：昨天咳嗽→肯定感冒了，用must；有能力分享笔记，用can 题型4答案 1. may come 思路：It’s possible that...=may+动词原形，表“可能做某事” 2. must be 思路：I’m sure that...=must+be/动词原形，表“肯定是/肯定做” 3. can’t finish 思路：It’s impossible that...=can’t+动词原形，表“不可能做” 4. must help 思路：have a duty to do=must do，表“必须做某事” 5. May; use 思路：Is it okay if I...=May I...，表委婉请求 6. can help 思路：be able to do=can do，表“能够做某事” 7. must be 思路：I’m certain that...=must+be/动词原形，表“肯定是” ( 1 ) 学科网（北京）股份有限公司 $