Unit 4 Helping out.语法精讲精练 2026-2027学年外研版英语八年级下册

该初中英语导学案聚焦外研版八下 Unit 4 情态动词表推测（对现在/将来），目标是帮助学生掌握 can、could、may、might、must 的语气强弱、句式适用及实际应用。通过“知识精讲（分模块解析）-典型例题（思路点拨）-综合演练（分层题型）”递进设计，结合语气阶梯表、句式对照表构建知识框架，形成连贯的学习路径。 亮点在于“语气阶梯表”直观呈现推测把握程度，“句式对照表”厘清肯否疑适用规则，分层练习（单选、填空、句型转换）覆盖基础到综合应用。例题精讲引导学生分析推测逻辑，培养思维品质，完成句子题型提升语言表达能力。答案解析详细，为教师提供教学反馈支持，助力学生系统掌握语法，发展学习能力。

外研版八下 Unit 4 Helping out.语法精讲精练 —— 情态动词(二)表推测(对现在 / 将来的推测)—— 使用说明 本讲承接情态动词(一),专门学习 can、could、may、might、must 表示推测的用法。这些情态动词表推测时没有人称和数的变化,只有语气强弱之分,后接动词原形。本讲为同步新授版,只讨论对现在或将来情况的推测(情态动词 + 动词原形),重点厘清每个词能用于肯定句、否定句还是疑问句,配套三类分层练习,答案与解析统一附于文末。 第一讲 知识精讲 一、什么是表推测 表推测就是说话人根据已有迹象,对某件事情发生的可能性做出判断。不同情态动词表示的把握程度不同,且后接动词原形(多为 be 或实义动词原形)。 The weather may / might be cold. Please take more clothes. 天气可能会冷,请多带些衣服。 把握程度(语气)由强到弱依次为: 语气阶梯 情态动词 含义 把握程度 最强(肯定) must 一定;准是 约 90% 以上,很有把握 中等 may 可能;也许 约 50%,不太确定 较弱 might / could 也许;或许 可能性更小,语气更委婉 最强(否定) can't 不可能 很有把握的否定 二、核心:各词能用于哪些句式(肯 / 否 / 疑) 表推测时,不同情态动词所能使用的句式不同,这是本讲的核心,也是中考命题关键。 情态动词 肯定句 否定句 疑问句 否定式含义 must √ 一定 (mustn't 表禁止,不表推测) — can (一般不用于肯定推测) √ can't 不可能 √ Can? 会是……吗 can't 不可能 could √ 可能 √ couldn't √ Could? couldn't 不可能 may √ 可能 √ may not 可能不 少用 may not 可能不 might √ 也许 √ might not 也许不 √(更委婉) might not 也许不 【易错警示】一句话记句式:must 只肯定,can 只否、疑,could / might 肯否疑都行。 三、may / might 表推测——也许、可能 may 和 might 都表示推测,意为「也许、可能」,否定形式在其后加 not,意为「可能不」。表示现在或将来的可能时,might 的可能性更小、语气更委婉。 My sister may / might not be at home. 我姐姐可能不在家。 You are not allowed to play with fire in the forest. It might kill plants, animals and even people. 森林里禁止玩火,那可能会烧死植物、动物甚至人。 Take an umbrella. It may rain later. 带把伞吧,待会儿可能下雨。 四、can 表推测——只用于否定句和疑问句 can 表推测时通常只用于否定句和疑问句,一般不用于肯定句(肯定句表推测多用 may/must)。 (一)疑问句:Can / Could? 会是……吗? Who sent the book? Can it be your mother? 谁送的书?会是你的妈妈吗? Whose bag is this? Could it be yours? 这是谁的包?会是你的吗? (二)否定句:can't 不可能(有把握的否定推测) I saw him in the office just now, so he can't be at home now. 我刚才在办公室看见他了,所以他现在不可能在家。 【易错警示】must(一定)的否定推测不是 mustn't,而是 can't(不可能);mustn't 表示「禁止」,不表推测。 五、could 表推测——肯、否、疑三种句式均可 could 表推测时,可用于肯定句、否定句和疑问句,表示某事有可能发生或可能是事实,语气比 can 委婉。 The flight could be delayed because of the heavy rain. 航班可能因为大雨而延误。(肯定句) Could it be possible to find the missing child? 有可能找到那个走失的孩子吗?(疑问句) 【注】could、might 表推测时不表示过去时,只表示语气比 can、may 更弱、更委婉。 六、must 表推测——只用于肯定句 must 表推测通常只用于肯定句,语气较肯定,表示把握性较大的推测,意为「一定、准是」。 The book must be Tom's, because his name is on it. 这本书一定是汤姆的,因为上面有他的名字。 The light is still on, so he must be at home. 灯还亮着,因此他一定在家。 You have worked all day. You must be tired. 你工作了一整天,一定累了。 七、肯定推测与否定推测的配对 把握 肯定推测 否定推测 例句对照 很有把握 must 一定 can't 不可能 He must be home. / He can't be home. 不太确定 may 可能 may not 可能不 He may be home. / He may not be home. 更没把握 might/could 也许 might not 也许不 He might be home. / He might not be home. 【注】解题步骤:先看句式(肯定/否定/疑问)排除不能用的词,再看把握程度(迹象是否充分)选语气强弱。 八、典型例题精讲 【例1】The light is still on, so he be at home. A. must B. can't C. need D. mustn't 【答案】A 【解析】「灯还亮着」是充分迹象,肯定句中有把握的肯定推测用 must;mustn't 表禁止不表推测,选 A。 【例2】I saw him in the office just now, so he be at home now. A. must B. can't C. may D. need 【答案】B 【解析】刚才还在办公室,现在不可能在家,有把握的否定推测用 can't,选 B。 【例3】—Who sent the book? — it be your mother? A. Must B. Can C. Need D. Should 【答案】B 【解析】疑问句表推测「会是……吗」用 Can/Could;must 不用于疑问推测,选 B。 【例4】I'm not sure. He be sleeping, but I'm not certain. A. must B. might C. can't D. need 【答案】B 【解析】I'm not sure / not certain 表明把握很小,用语气最弱的 might,选 B。 第二讲 综合演练 题型一 单项选择(每小题1分,共15分) 1. The light is on. He be at home. A. must B. can't C. need D. mustn't 2. I saw him in the office just now, so he be at home now. A. must B. can't C. may D. need 3. —Whose bag is this? —It be Tom's. His name is on it. A. can't B. must C. might D. need 4. I'm not sure. She be in the library. A. must B. may C. can't D. need 5. Who sent the book? it be your mother? A. Must B. Can C. Need D. Should 6. Don't play with fire in the forest. It kill plants and animals. A. must B. might C. need D. should 7. The weather be cold. Please take more clothes. A. may B. mustn't C. need D. should 8. He be American. He speaks with a strong French accent. A. must B. can't C. may D. need 9. The flight be delayed because of the heavy rain. A. must B. could C. need D. should 10. —Is that Mr. Li over there? —It be him. He has gone to Beijing. A. must B. can't C. may D. would 11. I'm not quite sure. My sister not be at home now. A. must B. might C. can D. need 12. The book be Tom's, because his name is on it. A. must B. can't C. need D. mustn't 13. it be possible to find the missing child? A. Must B. Could C. Need D. Should 14. He didn't answer the phone. He be sleeping, but I'm not sure. A. must B. might C. can't D. need 15. You have worked all day. You be tired. A. must B. can't C. needn't D. might 题型二 用 must / may / might / could / can't 填空(每小题1分,共14分) 1. The light is still on, so he be at home. 2. I saw him just now, so he be at home now. 3. The book be Tom's; his name is on it. 4. I'm not sure. She be in the library. 5. it be your mother who sent the book? 6. The flight be delayed because of the heavy rain. 7. He has gone to Beijing, so he be here now. 8. Take an umbrella. It rain later. 9. You have worked all day. You be tired. 10. I'm not quite sure. My sister not be at home. 11. it be possible to finish the work today? 12. He didn't answer; he be sleeping, but I'm not sure. 13. Don't touch it. It be dangerous. 14. That be our teacher—our teacher is much taller. 题型三 完成句子 / 句型转换(每小题2分,共10题) A. 根据汉语意思完成句子(1—5题,每空一词) 1. 灯还亮着,他一定在家。 The light is still on, so he at home. 2. 我刚才在办公室看见他了,他现在不可能在家。 I saw him in the office just now, so he at home now. 3. 我不确定,我姐姐可能不在家。 I'm not sure. My sister be at home. 4. 这会是你的妈妈吗? be your mother? 5. 航班可能因大雨而延误。 The flight delayed because of the heavy rain. B. 句型转换(6—10题,每空一词,用情态动词表推测改写) 6. Maybe he is at home. He at home. 7. It's impossible that he is at home. He at home. 8. I'm sure that the book is Tom's. The book Tom's. 9. Perhaps it will rain this afternoon. It this afternoon. 10. It is possible that she is in the library. She in the library. 答案与解析 题型一 单项选择 1. 【答案】A 【解析】灯亮是充分迹象,肯定句有把握推测 must 2. 【答案】B 【解析】刚在办公室,现在不可能在家,can't 3. 【答案】B 【解析】名字在上面,一定是 Tom 的,must 4. 【答案】B 【解析】I'm not sure 不确定,may 可能 5. 【答案】B 【解析】疑问句表推测「会是……吗」用 Can 6. 【答案】B 【解析】也许会烧死,委婉推测 might 7. 【答案】A 【解析】可能冷,may be 8. 【答案】B 【解析】法国口音重,不可能是美国人,can't 9. 【答案】B 【解析】肯定句中语气较弱的推测,could 10. 【答案】B 【解析】已去北京,不可能是他,can't 11. 【答案】B 【解析】might not 也许不,把握很小 12. 【答案】A 【解析】名字在上面,must be,mustn't 不表推测 13. 【答案】B 【解析】疑问句委婉推测 Could 14. 【答案】B 【解析】没接电话且不确定,might 也许 15. 【答案】A 【解析】工作一整天一定累,must 题型二 选词填空 1. 【答案】must 【解析】灯亮,有把握肯定 2. 【答案】can't 【解析】刚见过,不可能 3. 【答案】must 【解析】名字在上,一定 4. 【答案】may / might 【解析】不确定,可能 5. 【答案】Can 【解析】疑问句表推测,首字母大写 6. 【答案】could / might 【解析】肯定句委婉推测 7. 【答案】can't 【解析】已去北京,不可能在这 8. 【答案】may / might 【解析】将来可能,也许 9. 【答案】must 【解析】工作一整天,一定累 10. 【答案】might / may 【解析】might not 也许不 11. 【答案】Could / Can 【解析】疑问句,首字母大写 12. 【答案】might 【解析】不确定,也许正在睡 13. 【答案】may / might / could 【解析】可能危险 14. 【答案】can't 【解析】老师更高,所以不可能 题型三 完成句子 / 句型转换 1. 【答案】must be 【解析】有把握肯定推测 must + be 2. 【答案】can't be 【解析】有把握否定推测 can't + be 3. 【答案】might / may not 【解析】可能不,might not / may not 4. 【答案】Can it 【解析】疑问句推测 Can + 主语 it + be 5. 【答案】could be 【解析】肯定句委婉推测 could + be 6. 【答案】may be 【解析】Maybe = may be,可能 7. 【答案】can't be 【解析】impossible 对应 can't be 8. 【答案】must be 【解析】I'm sure 对应有把握的 must be 9. 【答案】might rain 【解析】Perhaps 对应 might + 动词原形 rain 10. 【答案】could be 【解析】possible 对应 could + be 学科网(北京)股份有限公司 $