Unit 4 Helping out 语法：情态动词讲义（专项练习） - 2025-2026学年外研版八年级下册英语

本讲义聚焦初中英语情态动词表推测的核心知识点，系统梳理may/might（可能性差异）、can/could（否定句疑问句及肯定句用法，can't表不可能）、must（肯定句表肯定推测）的用法，通过例句对比构建知识支架，帮助学生区分不同情态动词的推测语气和使用场景。 该资料以多样化练习（单选、填空、情景对话等）为特色，结合“礼物是谁送的”“房间灯亮是否在家”等具体语境，提升语言能力。通过must与can't的反义对比练习培养思维品质，分层设计助力学生巩固，课中辅助教师高效讲解，课后帮助学生查漏补缺，提升学习能力。

2026春季新版八年级下册外研版Unit 4 Helping out 语法讲义 Grammar：情态动词精讲精练 当我们想表达可能发生某事以及某人可能做某事时，可以用may / might表示。 例如: Bring a map because you may want to travel around. 带张地图，因为你可能想四处转转。 There may be a few showers, so bring an umbrella with you. 可能会有阵雨，所以随身带把伞吧。 在表示现在或将来的可能情况时，might表示的可能性比may表示的可能性要小一些。 例如:Take your swimming clothes because you might want to go swimming in the sea. 带上游泳衣吧，说不定你想到海里游泳呢。 情态动词can和could除了表示“能够，可以”等意义之外，还可以表示对现在或将来的推测，意为“会，可能”。但can表示推测时，往往用于否定句和疑问句。用于疑问句时，can比could表示的可能性要大; 用于否定句时, cannot (can't) 表示“不可能”。 例如:You can't be serious! 你不是认真的吧! could则可用于肯定句、否定句和疑问句。在以下例句中, can和could均表示“可能”: He could be in pain. 他可能很疼。 That could be harmful! 那可能有害! Can / Could this be true? 这有可能是真的吗? 情态动词must也可以表示猜测，意为“一定，肯定”，通常只用于肯定句。例如: Betty, you must know! Betty, 你肯定知道! 请仔细对比下面一组句子: -Who sent the present? Can it be your brother? 是谁送来的礼物啊？会是你哥哥吗?(询问可能性) -It must be your brother. I saw him in your room just now. 肯定是你哥哥,我刚才看见他在你的房间里。(语气强烈, 表示非常肯定) -It can't be my brother. He is still in France. 不可能是我哥哥, 他还在法国呢。(表示不可能) 外研版八年级下册Unit 4 情态动词专项练习 一、单项选择 ( ) 1. —Where is Tom? —He ______ in the library. He likes reading there after school. A. must be B. can't be C. might be D. need be ( ) 2. —Is that Mr. Li over there? —It ______ be him. He has gone to Beijing on business. A. mustn't B. can't C. may not D. shouldn't ( ) 3. The light is on in her room. She ______ be at home now. A. can B. must C. can't D. might ( ) 4. —______ the story be true? —No, it can't be true. It sounds impossible. A. Can B. Must C. Need D. Should ( ) 5. You ______ bring your camera, because you ______ want to take photos of the beautiful park. A. can; must B. must; can C. may; might D. might; must ( ) 6. —Who is knocking at the door? —It ______ be my dad. He said he would come back this afternoon. A. can B. must C. can't D. might ( ) 7. This medicine ______ be harmful if you take too much. You must follow the doctor's advice. A. can B. must C. can't D. need ( ) 8. —The classroom is empty. Where are the students? —They ______ be in the playground. They often play basketball there at this time. A. must B. can't C. might D. need ( ) 9. —Look! The girl in red ______ be Lucy. —No, it ______ be her. Lucy has gone to Shanghai. A. must; can't B. can; mustn't C. may; needn't D. can't; must ( ) 10. Take an umbrella with you. It ______ rain this afternoon. The weather report says there is a small chance of rain. A. must B. can C. might D. can't 二、用 must, might, could, can't 填空 1. The phone is ringing, but no one answers. They ______ be at home. 2. The ground is all wet. It ______ have rained last night. 3. She hasn't contacted us for three days. She ______ be in trouble, but we're not sure. 4. That ______ be my textbook. Mine is in my schoolbag. 5. You ______ be tired after working for ten hours without a rest. 6. —Is that the new student? —It ______ be her. I saw her name on the class list just now. 7. The noise next door ______ be from the children playing. They usually play there at this time. 8. He ______ be in the office. The light is off and the door is locked. 9. —______ this be the right way to the station? —I'm not sure. We can ask the policeman over there. 10. Don't worry. It ______ be a serious problem. It's probably just a small mistake. 三、句型转换（保持句意不变） 1. I am sure that he is in the classroom now. He ______ ______ in the classroom now. 2. It is impossible that he has finished the work in such a short time. He ______ ______ finished the work in such a short time. 3. Perhaps she will come to the party tonight. She ______ come to the party tonight. 4. Is it possible that they are having a meeting now? ______ they ______ having a meeting now? 5. I'm not sure if this is the correct answer. This ______ be the correct answer. 四、情景对话（补全对话，每空一词） A: Look! Someone is standing at the school gate. ______ it be our new teacher? B: It ______ be her. She told me she would come at 9:00, but it's only 8:30 now. A: Then who ______ it be? B: It ______ be your father. He said he would come to see you today. A: No, it ______ be him. He is still in Shanghai on business. B: Oh, it ______ be the gatekeeper. He often stands there early in the morning. A: You're right! That must be him. 五、句子翻译（使用情态动词表推测） 1. 这本书一定是她的。上面有她的名字。 ___________________________________________________ 2. 他不可能在家，因为他的车不在外面。 ___________________________________________________ 3. 明天可能会下雨，所以你最好带把伞。 ___________________________________________________ 4. 这可能不是一个好主意，我们再想想吧。 ___________________________________________________ 5. ——那个穿蓝色衣服的女孩是谁？ ——可能是我的妹妹，也可能不是，我不太确定。 ___________________________________________________ ___________________________________________________ 学科网（北京）股份有限公司 $ 外研版八年级下册 Unit 4 情态动词专项练习 答案+逐题解析 一、单项选择 1. A 解析：后文说他放学后喜欢在那里看书，语气非常肯定，用must be（一定在）。 2. B 解析：他去北京出差了，所以“不可能”是他，can’t 表示否定推测“不可能”。 3. B 解析：房间灯亮着，很肯定她在家，用must。 4. A 解析：疑问句中表推测用Can（可能……吗？）。 5. C 解析：前半句“你可以带相机”，后半句“你可能想拍照”，可能性不大，用may; might。 6. B 解析：爸爸说过今天下午回来，很肯定，用must。 7. A 解析：can 用于肯定句表理论上的可能“这种药吃多可能有害”。 8. A 解析：这个时间他们常去操场打球，很肯定，用must。 9. A 解析：第一空肯定猜测用must；第二空Lucy去上海了，不可能是她，用can’t。 10. C 解析：天气预报说下雨可能性小，用might（可能，可能性较低）。 二、用 must, might, could, can't 填空 1. can’t 解析：电话响没人接，不可能在家。 2. must 解析：地面全湿了，一定昨晚下雨了。 3. might/could 解析：不确定，可能遇到麻烦。 4. can’t 解析：我的书在书包里，不可能是我的。 5. must 解析：连续工作10小时，一定很累。 6. must 解析：刚在名单上看到名字，一定是她。 7. must 解析：这个时间孩子常在这里玩，一定是他们。 8. can’t 解析：灯关着门锁了，不可能在办公室。 9. Could/Can 解析：疑问句表推测“这可能是去车站的路吗？”。 10. can’t 解析：只是小错误，不可能是严重问题。 三、句型转换 1. must be 解析：I am sure = must（肯定推测）。 2. can’t have 解析：impossible = can’t（不可能）。 3. may/might 解析：perhaps = may/might（可能）。 4. Can; be 解析：Is it possible = Can…be…。 5. might/could 解析：not sure = might/could（可能）。 四、情景对话 1. Can（疑问句表推测） 2. can’t（时间没到，不可能） 3. can（可能是谁） 4. must（爸爸说过来看你，一定是） 5. can’t（在上海出差，不可能） 6. must（门卫常站在那里，一定是） 五、句子翻译 1. This book must be hers. There is her name on it. 解析：有名字→肯定推测用must。 2. He can’t be at home because his car isn’t outside. 解析：车不在→不可能在家，用can’t。 3. It may/might rain tomorrow, so you’d better take an umbrella. 解析：可能下雨→may/might。 4. This may not be a good idea. Let’s think again. 解析：可能不是→may not。 5. —Who is the girl in blue? —It may/might be my sister. I’m not sure. 解析：不确定→may/might。 学科网（北京）股份有限公司 $