KET 语法库

情态动词 Modal Verbs

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情态动词 Modal Verbs

考试：📘 KET ✓ 📙 PET ✓ 📕 FCE·雅思 ✓ 分类：词法 考试入口：KET语法清单 | PET语法清单 关联：一般现在时 Simple Present | 条件句 Conditionals

核心规则（Grammar Core）

情态动词的共同特征

  1. 后面跟动词原形（不加 to，不加 s）
  2. 否定直接加 not（can’t, mustn’t, shouldn’t）
  3. 疑问直接提前（Can you…? Must I…?）
  4. 没有 -s/-ed/-ing 形式——cans, musted, shoulding 全部 ❌

KET 必会的情态动词

情态动词核心含义例句
can能力 / 许可I can swim. / You can go now.
can’t不能 / 禁止She can’t drive yet.
could过去的能力 / 礼貌请求I could read at age 4. / Could you help me?
must必须（强制）You must wear a seatbelt.
mustn’t禁止You mustn’t run in the corridor.
should应该（建议）You should see a doctor.
shouldn’t不应该You shouldn’t eat too much sugar.

PET 扩展的情态动词

情态动词核心含义例句
might可能（不确定）It might rain later.
may可能 / 正式许可May I come in?
have to不得不（外部要求）I have to finish this by Friday.
don’t have to不必（不强制）You don’t have to come if you’re busy.
ought to应该（≈should）You ought to apologize.

Grammar Lens

must vs have to vs should ⚠️（KET/PET 高频）

语气强度来源否定含义
must最强 💪说话人自己决定mustn’t = 禁止！
have to强外部规则/情况don’t have to = 不必
should中等建议shouldn’t = 不应该

关键区别：

mustn't ≠ don't have to ⚠️⚠️⚠️

You mustn't smoke here.     = 禁止！在这里抽烟是违法的。
You don't have to come.     = 不必来，来不来随你。

mustn't = 绝对不可以
don't have to = 可以不做（没有强制要求）

这是 KET/PET 的黄金考点。

can vs could · 礼貌程度

Can you help me?      ← 普通请求，朋友之间
Could you help me?    ← 更礼貌，对老师或陌生人
Would you mind helping me? ← 最礼貌（📙 PET）

Culture Note 🇬🇧 英国人以礼貌著称。在英国，即使是最简单的请求也会用 could： “Could I have a cup of tea, please?”（而不是 “Give me tea.“） 书虫里英国角色的对话充满了 could、would、might——这不是他们不确定，而是在表达礼貌。

情态动词表推测（📙 PET → 📕 FCE）

确定程度肯定推测否定推测
100% 肯定must becan’t be
很可能should beshouldn’t be
可能may/might bemay/might not be

“He must be tired — he’s been working all day.”（他一定很累） “She can’t be at home — I just saw her at the shop.”（她不可能在家）

😂 Grammar Joke

mustn't vs don't have to · 一则校园故事

A new student asks the teacher about the school rules:

Student: “Must I wear a uniform?” Teacher: “Yes, you must.” Student: “Can I use my phone in class?” Teacher: “No, you can’t.” Student: “Should I do homework every day?” Teacher: “You should, yes.” Student: “Must I come to school on Saturday?” Teacher: “No, you don’t have to.” Student: “Great! So I mustn’t come on Saturday?” Teacher: “No! Mustn’t means it’s forbidden. Don’t have to means it’s your choice. You don’t have to come, but you can if you want.” Student: “I think I’ll stay home.”

这个新生刚好把 mustn’t（禁止）和 don’t have to（不必）搞混了——这也是 KET 最爱考的陷阱。

🏛 语言文化光点

“Keep Calm and Carry On” 的情态动词故事

1939年，英国政府为了应对德国空袭，印了一批海报。最有名的一张写着：

Keep calm and carry on.

这里没有情态动词——它用的是祈使句（直接命令）。但英国人当时觉得太直接了，所以这批海报从没公开使用过。

直到2000年，一家二手书店偶然发现了一张原版，它才火遍全球。如果当年英国政府用了情态动词：“You should keep calm” 或 “You might want to carry on”——就不会有今天的文化标志了。

有时候，不用情态动词反而更有力量。

例题精讲

例1（📘 KET · must vs mustn’t）

You _____ be quiet in the library. You _____ talk loudly.

答案：must, mustn’t。图书馆 = 必须安静 + 禁止大声说话。

例2（📘 KET · mustn’t vs don’t have to）

Tomorrow is a holiday. You _____ go to school.

答案：don’t have to。假期 = 不必去（不是禁止去）。

例3（📘 KET · could 礼貌请求）

— _____ you tell me the way to the station, please?

答案：Could。对陌生人问路 → 用 could 更礼貌。

例4（📙 PET · 推测）

Tom isn’t answering his phone. He _____ be in a meeting.

A. must B. can’t C. should D. might

答案：D（might = 可能。不确定，只是猜测）。如果有更强证据（比如看到他的日历），可以用 must。

例5（📙 PET · Writing 建议信）

Dear Tom, I think you should try the new Italian restaurant. You must try their pizza — it’s the best! You don’t have to book a table on weekdays, but you might need to wait on weekends.

一封短信里混用了4种情态动词，PET 写作加分。

📖 Real English · 真实阅读

🔵 Rules at the Louvre Museum, Paris

Welcome to the Louvre! Before you enter, please read our rules. You must buy a ticket online or at the entrance. Children under 18 don’t have to pay. You can take photos, but you mustn’t use a flash — it can damage the paintings. You should arrive early because the queue can be very long. You shouldn’t touch any artwork. You may bring a small bag, but large backpacks must be left at the cloakroom. The Mona Lisa might be crowded — you should visit it first thing in the morning.

🔵 Could You Survive on Mars?

Life on Mars would be extremely difficult. You couldn’t breathe the air — Mars has almost no oxygen. You would have to wear a spacesuit every time you went outside. You could grow some food in special greenhouses, but you wouldn’t be able to grow enough for a balanced diet. Water might exist underground, but scientists can’t be sure yet. Temperatures can drop to minus 60°C, so you would need excellent heating. Could humans really live there? NASA believes we can — but it may take decades to make it happen.

🔵 A Doctor’s Advice

“You should exercise at least 30 minutes a day,” says Dr. Chen. “You don’t have to join a gym — you can just walk. You shouldn’t sit for more than two hours without moving. You must drink enough water — most people don’t. You mustn’t skip breakfast; your brain can’t work properly without fuel. And you ought to sleep at least eight hours. I know you might think you can survive on five, but you can’t — not without paying a price later.”

练习题

📘 KET 基础（5题）

  1. I _____ speak three languages: Chinese, English, and French.（can / must）
  2. You _____ touch that! It’s very hot.（mustn’t / don’t have to）
  3. She _____ swim when she was five years old.（can / could）
  4. You look tired. You _____ go to bed early tonight.（should / must）
  5. _____ I use your phone, please?（May / Must）

📙 PET 进阶（3题）

  1. 填空：You _____ come to the party if you don’t want to. It’s your choice.
  2. 推测：That _____ (not / be) Tom’s car. Tom drives a blue car, and that one is red.
  3. 改写成更礼貌版本：Open the window. → _____ you _____ the window, please?

🔗 节点关系

情态动词 ──────┬─ can/could → 能力、许可、请求
               ├─ must/have to → 义务、禁止
               ├─ should/ought to → 建议
               ├─ might/may → 可能性
               ├─ 条件句（If..., you should/could...）
               └─ 推测（must be / can't be · 📙 PET）

双链跳转： 条件句 Conditionals | 一般现在时 Simple Present | 疑问句 Questions

Code & Rob · K12英语语法库 · KET/PET, 2026

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