威威老師的文法特快車：基本助動詞 (Basic Modal Verbs)
課程導航
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哈囉各位同學！我是威威老師。
來，看下面四句話：
- You can go now.
- You may go now.
- You should go now.
- You must go now.
全部都是「你走吧」，但語氣完全不同——
- can = 「你可以走」（許可）
- may = 「你可以走」（更正式的許可）
- should = 「你最好走」（建議）
- must = 「你必須走」（強制！）
英文助動詞就是語氣調節器——同一個句子加上不同的助動詞，意思和語氣完全變樣。學測克漏字最愛考的就是這個——選錯一個字，整題都錯。
今天威威老師帶你拆解 6 大基本助動詞——加上它們的「過去推測版」（modal + have + V-pp），總共12 種語氣一次學會。
繫好安全帶 🚂
課前快問 (Pre-Quiz) — 複習 10 疑問句與否定句
- ____ she go to school yesterday?（Do / Does / Did）
- You don’t like spicy food, ____?（do you / don’t you）
- He is from Japan, ____?（is he / isn’t he）
解答
- Did — yesterday → 過去式。
- do you — 前否後肯。
- isn’t he — 前肯後否。
一、助動詞的三大鐵律
在學各種用法之前，先記住這三條黃金規則：
| 鐵律 | 說明 | 範例 |
|---|---|---|
| 鐵律 1 | 助動詞後永遠接原形動詞 | She can swim.（不是 swims！） |
| 鐵律 2 | 助動詞沒有三單變化 | She can swim.（不是 cans！） |
| 鐵律 3 | 兩個助動詞不能連用 | ❌ will can → ✅ will be able to |
💡 威威核心：助動詞是「變色龍」，但它變的是「語氣」，不是「人稱」或「時態」。
二、Can / Could — 能力、可能性、禮貌請求
| 用法 | Can | Could |
|---|---|---|
| 能力 | I can speak English.（現在的能力） | I could swim at age 5.（過去的能力） |
| 請求許可 | Can I use your pen?（口語） | Could I use your pen?（更禮貌！） |
| 可能性 | It can get cold here.（一般可能） | It could rain.（較不確定） |
禮貌程度排名
🎵 Could I… > Can I… > May I…（May 最正式）
跟陌生人或長輩請求 → 用 Could 最安全（既禮貌又不會太老氣）。
Can 的特殊片語
| 片語 | 意思 | 例句 |
|---|---|---|
| can’t help + V-ing | 忍不住 | I can’t help laughing at his jokes. |
| can’t help but + V | 忍不住 | I can’t help but laugh. |
| can hardly | 幾乎不能 | I can hardly believe my eyes. |
| as … as one can | 盡可能… | Run as fast as you can! |
🎯 Can / Could 即時練習（5 題）
1. Choose: When I was a child, I ______ ride a bike without training wheels. (A) can (B) can’t (C) could (D) couldn’t
2. Choose: ______ I have a glass of water, please?（最有禮貌的版本） (A) Can (B) Could (C) May (D) Will
3. Translate: 「我忍不住想笑。」(Use can’t help)
4. 改錯：She cans speak three languages.
5. Choose: This problem ______ be solved by anyone. (A) can (B) cans (C) could to (D) is can
寫好答案再往下看 👇
解答與詳解
第 1 題：(C) could
✅ “When I was a child” → 過去 → 用 could（過去的能力）。
第 2 題：(B) Could
✅ Could 是現代英文最普及的禮貌請求形式。 💎 May I 也對，但較正式（適合非常正式場合）。
第 3 題：I can't help laughing.
✅ can’t help + V-ing = 忍不住做某事。 💎 也可說 I can’t help but laugh.（can’t help but + 原形 V）
第 4 題：cans → can
✅ 修正：She can speak three languages. 解析：can 沒有三單變化，沒有 cans 這個字！
第 5 題：(A) can
✅ This problem can be solved… 解析：被動語態 can + be + V-pp。 ❌ (B) cans 不存在。
三、May / Might — 許可與不確定的可能性
| 用法 | May | Might |
|---|---|---|
| 許可（正式） | May I come in?（請求進入） | ❌ 很少用 |
| 可能性 ~50% | She may be at home. | She might be at home.（差不多） |
| 可能性 ~30% | — | It might rain.（較不確定） |
| 祝福 | May you have a great year! | — |
May / Might 的回答
| 問句 | 肯定 | 否定 |
|---|---|---|
| May I come in? | Yes, you may / Of course | No, you may not / I’m afraid not |
🚨 常見錯誤： 用 could 回答 May 是錯的！「Yes, you could.」是錯誤回答。
🎯 May / Might 即時練習（5 題）
1. Choose: ______ I borrow your dictionary?（最正式） (A) May (B) Will (C) Should (D) Must
2. Choose: She didn’t answer the phone. She ______ be in a meeting. (A) must (B) might (C) can (D) should
3. Translate: 「明天可能會下雨。」(Use might)
4. Choose: “May I leave early today?” “Yes, you ______.” (A) can (B) could (C) may (D) might
5. Translate: 「祝你旅途愉快！」(Use May)
寫好答案再往下看 👇
解答與詳解
第 1 題：(A) May
✅ May I borrow…?（最正式的請求）。
第 2 題：(B) might
✅ She might be in a meeting. 解析：「可能在開會」→ 不確定的推測 → might。
第 3 題：It might rain tomorrow.
✅ might 表示不太確定的可能性。
第 4 題：(C) may
✅ Yes, you may.（正式回答 May 的問句） 💎 也可以回 “Of course.” / “Sure.”（口語）。
第 5 題：May you have a wonderful trip!
✅ May + 主詞 + 原形 V = 祝福句型。 💎 同類：May you live a long life!（祝你長壽！）
四、Must / Have to — 義務、必要、推測
4-1 must vs. have to 的差別
| Must | Have to | |
|---|---|---|
| 義務來源 | 說話者主觀的感覺 | 外在規定 / 法律 |
| 語氣 | 主觀，較強 | 客觀 |
| 例句 | I must finish this!（自己決心） | I have to wear a uniform.（學校規定） |
| 時態變化 | ❌ 沒過去式（用 had to 代替） | ✓ 有 had to / will have to |
4-2 ⚠️ 否定意思完全不同！
| 肯定 | 否定 | 意思 |
|---|---|---|
| must | must not (mustn’t) | 不可以（禁止！） |
| have to | don’t have to | 不必（不是禁止） |
🚨 超級陷阱：
- You mustn’t smoke here. = 你不可以在這裡抽菸（禁止！）
- You don’t have to come. = 你不必來（不是強制，可以不來）
這兩個意思完全相反，學測超愛考！
4-3 Must 的推測用法（高度肯定）
Must 不只是「必須」——還可以表達很肯定的推測：
| 例句 | 中文 |
|---|---|
| She must be tired. | 她一定很累（看起來累）。 |
| He must have forgotten. | 他一定是忘了（沒出現）。 |
| You must be joking! | 你一定在開玩笑！ |
4-4 推測強度排名
must be (~95%) > may/might be (~50%) > can't be (~0%, 不可能)
| 推測強度 | 助動詞 | 例句 |
|---|---|---|
| 最確定 | must | He must be the new boss. |
| 較確定 | should | He should be here by now. |
| 中等 | may | He may be at home. |
| 不確定 | might / could | He might be sick. |
| 不可能 | can’t | He can’t be the thief. |
🎯 Must / Have to 即時練習（5 題）
1. Choose: You ______ smoke in this building. It’s prohibited. (A) don’t have to (B) mustn’t (C) needn’t (D) couldn’t
2. Choose: You ______ bring food to the party. There will be plenty provided. (A) mustn’t (B) shouldn’t (C) don’t have to (D) can’t
3. Choose: She’s been studying for 10 hours. She ______ be exhausted. (A) can (B) should (C) must (D) would
4. Translate: 「我必須在 6 點前完成。」(Use must / have to)
5. Choose: He couldn’t have done it. He ______ at school then. (A) must be (B) must have been (C) might be (D) could be
寫好答案再往下看 👇
解答與詳解
第 1 題：(B) mustn't
✅ You mustn’t smoke.（禁止） 💎 ❌ “don’t have to” 是「不必」，不是「不可以」——意思完全不同！
第 2 題：(C) don't have to
✅ You don’t have to bring food.（不必，不是禁止） 💎 (A) mustn’t 會變成「禁止帶食物」，跟原意（不必）矛盾。
第 3 題：(C) must
✅ She must be exhausted.（很肯定的推測）
第 4 題：I must (have to) finish it by 6.
✅ 兩種寫法都對：
- I must finish it by 6.（自己強烈想完成）
- I have to finish it by 6.（外在期限要求）
第 5 題：(B) must have been
✅ He must have been at school then. 解析：「過去的肯定推測」→ must + have + V-pp。
五、Should — 建議、預期、悔恨
| 用法 | 例句 |
|---|---|
| 建議 | You should see a doctor. |
| 預期 | The train should arrive soon.（預計快到了） |
| 悔恨（should have + V-pp） | I should have studied harder.（當初應該更用功） |
| 批評（shouldn’t have + V-pp） | You shouldn’t have said that. |
Should 的強度比較
must（必須，最強）> should（應該）> had better（最好，帶警告）> could（可以，最弱）
| 強度 | 助動詞 | 例句 |
|---|---|---|
| 最強 | must | You must stop smoking. |
| 強 | should | You should stop smoking. |
| 中等（警告） | had better | You’d better stop smoking. |
| 弱 | could | You could try stopping. |
🎯 Should 即時練習（5 題）
1. Choose: You look tired. You ______ go to bed earlier tonight. (A) should (B) must (C) can (D) will
2. Translate: 「我當初應該更努力學習。」(Use should have)
3. Choose: She hasn’t come yet. She ______ have missed the bus. (A) must (B) might (C) should (D) Both A and B
4. Choose: You ______ told me about the meeting! (A) should (B) should have (C) must (D) had to
5. Translate: 「你不該那樣對她說話。」(Use shouldn’t have)
寫好答案再往下看 👇
解答與詳解
第 1 題：(A) should
✅ You should go to bed earlier.（建議）
第 2 題：I should have studied harder.
✅ should + have + V-pp = 過去應該做卻沒做（悔恨）。
第 3 題：(D) Both A and B
✅ 兩個都可以：
- She must have missed the bus.（很肯定）
- She might have missed the bus.（不太確定） 看你想表達多肯定的推測。
第 4 題：(B) should have
✅ You should have told me!（你當初應該告訴我！表悔恨/責備）
第 5 題：You shouldn't have spoken to her like that.
✅ shouldn’t + have + V-pp = 過去不應該做卻做了（批評）。
六、Will / Would — 未來、意願、過去習慣
| 用法 | Will | Would |
|---|---|---|
| 未來 | I will call you tomorrow. | — |
| 意願 | I will help you.（我願意） | I would help if I could.（有條件的意願） |
| 禮貌請求 | Will you open the door? | Would you open the door?（更禮貌） |
| 過去的習慣 | — | When young, I would play outside every day. |
| 拒絕 | He won’t listen.（他就是不聽） | — |
Would 的特殊用法
| 用法 | 例句 |
|---|---|
| would like to | I would like to order coffee.（想要） |
| would rather | I would rather stay home.（寧願） |
| would have + V-pp | I would have helped if I knew.（早知道我就…） |
🎯 Will / Would 即時練習（5 題）
1. Choose: I ______ call you as soon as I arrive. (A) will (B) would (C) shall (D) might
2. Choose: ______ you mind closing the window?（最禮貌） (A) Will (B) Would (C) Can (D) May
3. Translate: 「小時候我每天晚上都會跟我哥下棋。」(Use would)
4. Choose: I ______ rather stay at home tonight. (A) will (B) would (C) had (D) should
5. Translate: 「如果我早知道，我就會幫你了。」(Use would have)
寫好答案再往下看 👇
解答與詳解
第 1 題：(A) will
✅ I will call you…（一般未來）
第 2 題：(B) Would
✅ Would you mind…?（最禮貌的請求）。 💎 注意：Would you mind + V-ing。
第 3 題：When I was young, I would play chess with my brother every night.
✅ would 表「過去的習慣」（= used to）。
第 4 題：(B) would
✅ I would rather stay at home.（我寧願…）
第 5 題：If I had known, I would have helped you.
✅ would + have + V-pp 用於「過去的假設結果」（18 假設語氣 詳解）。
七、modal + have + V-pp — 過去推測 / 悔恨
這是學測超高頻考點！助動詞 + have + V-pp = 在「評論過去」發生的事。
| 結構 | 意思 | 例句 |
|---|---|---|
| must have + V-pp | 一定做過了 | She must have left already. |
| may have + V-pp | 可能做過了 | He may have forgotten. |
| might have + V-pp | 或許做過了 | They might have missed the bus. |
| could have + V-pp | 本可以做但沒做 | You could have told me! |
| should have + V-pp | 應該要做但沒做 | I should have studied. |
| shouldn’t have + V-pp | 不應該做但做了 | You shouldn’t have said that. |
| would have + V-pp | 早知道就會…（沒發生） | I would have helped if I knew. |
| can’t have + V-pp | 不可能做了 | He can’t have done this. |
💡 威威記法：「modal + have + V-pp」永遠在說「過去發生（或沒發生）」的事，配上一個「評論的口氣」：
- must have：「一定」
- may/might have：「可能」
- should have：「應該（但沒）」
- could have：「本可以（但沒）」
- would have：「早知道就會」
八、考試陷阱大整理
學測助動詞考題的 5 大陷阱
陷阱 1：mustn’t vs. don’t have to（意思相反！）
- mustn’t = 禁止
- don’t have to = 不必
陷阱 2：助動詞後永遠接原形
❌ She can swims. / He must goes. ✅ She can swim. / He must go.
陷阱 3：兩個助動詞不能連用
❌ will can → ✅ will be able to ❌ must can → ✅ must be able to
陷阱 4：should have / could have / must have 的差別
看上下文判斷是「悔恨」「未做的事」還是「肯定的推測」。
陷阱 5：can’t / couldn’t 兩種否定推測
can’t = 不可能（很肯定否定） couldn’t have = 過去不可能（曾發生過某事但被質疑）
章末總測驗 (Chapter Test) — 30 題
🟢 基礎題 (1-10)
1. You ______ smoke in this building. It’s against the rules. (A) don’t have to (B) mustn’t (C) needn’t (D) couldn’t
2. When I was a child, I ______ ride a bike without training wheels. (A) can (B) can’t (C) couldn’t (D) may not
3. ______ I borrow your dictionary for a moment? (A) Will (B) Should (C) Must (D) May
4. You look tired. You ______ go to bed earlier tonight. (A) should (B) must (C) can (D) will
5. She’s been studying for 10 hours straight. She ______ be exhausted. (A) can (B) should (C) must (D) would
6. ______ you please pass me the salt? (A) Will (B) May (C) Must (D) Should
7. I ______ swim when I was 5, but now I’m great. (A) can’t (B) couldn’t (C) won’t (D) shouldn’t
8. Take an umbrella. It ______ rain later. (A) must (B) should (C) might (D) shouldn’t
9. You ______ wear a uniform at this school. (A) have to (B) might (C) could (D) should
10. ______ you mind opening the window? (A) Will (B) Would (C) Can (D) Both A and B
🟡 進階題 (11-20)
11. You ______ me earlier. I could have helped you. (A) should tell (B) should have told (C) must tell (D) had to tell
12. The lights are off. They ______ to bed already. (A) must go (B) should go (C) must have gone (D) should have gone
13. You ______ bring food to the party. There will be plenty provided. (A) mustn’t (B) shouldn’t (C) don’t have to (D) can’t
14. I’m not sure where she is. She ______ be at the library. (A) must (B) might (C) can (D) will
15. He ______ have stolen the money. He was with me all evening. (A) must (B) might (C) should (D) can’t
16. I ______ rather drink tea than coffee. (A) will (B) would (C) had (D) should
17. He ______ have been here by now. The traffic must be bad. (A) should (B) must (C) can (D) might
18. You ______ have seen the movie. It’s playing only in 3 cities. (A) couldn’t (B) shouldn’t (C) mustn’t (D) needn’t
19. I ______ help you if I had time, but I’m busy now. (A) will (B) would (C) should (D) might
20. Choose: She ______ to school every day.（一般動詞，主詞三單） (A) musts go (B) must goes (C) must go (D) musts to go
🔴 挑戰題 (21-30)
21. Translate three sentences: (a) 「你應該早點告訴我！」 (b) 「他可能已經離開了。」 (c) 「你不必帶禮物。」
22. Find errors: (a) “She cans speak Spanish.” (b) “You musts go now.” (c) “I will can swim soon.”
23. Replace with proper modal + have + V-pp: (a) “I’m sure he forgot.” → He ______ (b) “I regret not studying.” → I ______ (c) “It’s impossible that she did that.” → She ______
24. Choose all correct: (A) You shouldn’t to smoke. (B) You shouldn’t smoke. (C) She might be at home. (D) She mights be at home.
25. Distinguish meaning: (a) “You mustn’t go.” vs. “You don’t have to go.” (b) “He must be tired.” vs. “He must have been tired.” (c) “I should call her.” vs. “I should have called her.”
26. Translate: (a) 「我們真的應該節省用水。」(Use should + save water) (b) 「她當初不該那樣說的。」(Use shouldn’t have said) (c) 「他可能會晚點到。」(Use might + arrive)
27. Choose the most polite request: (A) Get me some water. (B) Can you get me water? (C) Could you please get me some water? (D) Would you mind getting me some water?
28. Identify the function of the modal: (a) “He must be a doctor.” (能力 / 義務 / 推測 / 建議) (b) “You must finish your homework.” (能力 / 義務 / 推測 / 建議) (c) “Could you help me?” (能力 / 許可 / 推測 / 請求) (d) “She could swim at 4.” (能力 / 許可 / 推測 / 請求)
29. Translate: (a) 「妳一定餓了。」(must + 推測) (b) 「我寧願不去。」(would rather not) (c) 「他本來可以贏的。」(could have won)
30. Terminal challenge—rewrite fixing all errors: “You musts to study harder. If you don’t, you couldn’t pass the exam. Last time, you should studied more, but you played video games instead. Now you don’t has to fail again—you can wills do it!”
章末總測驗 解答與詳解
🟢 基礎題 解答
第 1 題：(B) mustn't — 規定禁止 → mustn't。
第 2 題：(C) couldn't — 過去能力否定 → couldn't。
第 3 題：(D) May — 正式請求許可。
第 4 題：(A) should — 建議。
第 5 題：(C) must — 很肯定推測。
第 6 題：(A) Will — 禮貌請求 (Will you...?)。
第 7 題：(B) couldn't — 「5 歲時不會」→ 過去能力否定。
第 8 題：(C) might — 「可能下雨」→ 不確定的推測。
第 9 題：(A) have to — 學校規定 → 客觀義務。
第 10 題：(D) Both A and B — Will/Would you mind...? 都對，Would 更禮貌。
🟡 進階題 解答
第 11 題：(B) should have told
「當初應該告訴我」（沒做）→ should have + V-pp。
第 12 題：(C) must have gone
「燈關了，一定睡了」→ 過去的肯定推測 → must have + V-pp。
第 13 題：(C) don't have to
「不必帶」→ don’t have to。
第 14 題：(B) might
「可能在圖書館」→ 不確定推測 → might。
第 15 題：(D) can't
「不可能偷錢」→ can’t（最強的否定推測）。
第 16 題：(B) would
would rather = 寧願。
第 17 題：(A) should
「他應該到了」→ 預期 → should。
第 18 題：(A) couldn't
「不可能看過」→ couldn’t have + V-pp。
第 19 題：(B) would
「如果我有時間就會幫你」→ 假設語氣 → would。
第 20 題：(C) must go
助動詞沒三單變化 + 後接原形 → must go。
🔴 挑戰題 解答
第 21 題：翻譯
(a) You should have told me earlier! (b) He may/might have already left. (c) You don’t have to bring a gift.
第 22 題：找錯
(a) cans → can（沒三單變化） (b) musts → must（沒三單變化） (c) will can → will be able to（兩助動詞不能連用）
第 23 題：
(a) He must have forgotten.（「一定忘了」） (b) I should have studied.（「悔恨沒讀書」） (c) She can’t have done that.（「不可能做了」）
第 24 題：(B)(C) 正確
(A) ✗ shouldn’t 後不加 to。 (B) ✓ shouldn’t smoke（原形動詞）。 (C) ✓ might be at home。 (D) ✗ might 沒有三單變化（mights 不存在）。
第 25 題：意思區辨
(a) “mustn’t go” = 禁止去；“don’t have to go” = 不必去（兩個意思相反！） (b) “must be tired” = 現在一定很累；“must have been tired” = 過去一定很累（時間不同） (c) “should call” = 應該打電話（還沒打）；“should have called” = 應該打卻沒打（悔恨）
第 26 題：翻譯
(a) We should really save water. (b) She shouldn’t have said that. (c) He might arrive late.
第 27 題：(D)
“Would you mind + V-ing?” 是英文中最禮貌的請求方式。 禮貌排序：(A) 命令最不禮貌 < (B) Can you 一般 < (C) Could you please 禮貌 < (D) Would you mind 最禮貌。
第 28 題：
(a) 推測（“他一定是醫生” — 從外觀推斷） (b) 義務（必須完成功課） (c) 請求（禮貌的請求協助） (d) 能力（4 歲就會游泳）
第 29 題：翻譯
(a) You must be hungry. (b) I would rather not go. （或 I’d rather not go.） (c) He could have won.
第 30 題：完整修正
原段：You musts to study harder. If you don’t, you couldn’t pass the exam. Last time, you should studied more, but you played video games instead. Now you don’t has to fail again—you can wills do it!
✅ 修正版： “You must study harder. If you don’t, you won’t pass the exam. Last time, you should have studied more, but you played video games instead. Now you don’t have to fail again—you can definitely / surely do it!”
修正了 5 處：
- musts to → must（沒三單，後不加 to）
- couldn’t → won’t（未來條件 → won’t；如果原意是「不可能通過」，要說 won’t be able to pass）
- should studied → should have studied（過去悔恨）
- don’t has to → don’t have to（don’t + 原形 have）
- can wills → can definitely（兩助動詞不能連用，改用副詞加強語氣）
課前快問 解答
詳見前面解答區。
自我評分
| 分數（30 題） | 等級 | 建議 |
|---|---|---|
| 27-30 | 🏆 威威等級 | 助動詞精通！進入 12 被動語態。 |
| 22-26 | 🥈 穩健等級 | 重點複習：mustn’t vs. don’t have to、modal + have + V-pp。 |
| 16-21 | 🥉 加油等級 | 把「6 大助動詞速查表」 + 「過去推測表」背熟。 |
| 0-15 | 💪 再出發 | 從三大鐵律開始：助動詞後接原形、沒三單、不能連用。 |
複習計畫
時間 內容 今天 全文 + 即時練習 + 章末測驗 第 3 天 重做錯題 + 默寫 modal + have + V-pp 表格 第 7 天 用 5 個朋友的近況練習推測（She must be busy / He might have…） 第 14 天 翻譯 5 個悔恨句（I should have… I shouldn’t have…） 考試前 重看「5 大陷阱」+ 推測強度排名
學習科學小知識：交替練習 (Interleaving)
不要一次只練 must、再一次只練 should——把它們混在一起練！
研究 (Rohrer et al., 2015) 顯示：混合不同類型的題目雖然當下感覺較難，但長期記憶效果好 40%。
為什麼？每遇到一題你都得先判斷類型（這是必須？應該？能力？許可？）——這個判斷動作本身就是學習。考場上每題都要重新判斷，平時練習就要訓練這個反射。
所以，不要一次學一個助動詞，要6 個一起練！威威老師為什麼把 6 個助動詞混在 30 題裡？就是這個原理。
上一篇： 10 疑問句與否定句 下一篇： 12 被動語態 相關主題： 18 假設語氣 | 20 助動詞詳解