一句话：must 是"说话人主观觉得必须"，have to 是"客观情况迫使不得不"。两个都翻译成"必须/得"，但出发点不同。
妈妈说"You must study hard"——这是妈妈的要求（主观命令）。"You have to pass many exams"——考试是客观门槛，谁也绕不开。
最关键的一对反义词：mustn't = 禁止（千万别做），don't have to = 不必（可做可不做）。KET 完形最爱考这对。
为什么它是 KET 高频考点学校规则、职业要求、家庭规矩全靠它说。KET 完形 Part 5 几乎每年都有一空考 mustn't vs don't have to，口语 Part 1 也常问 "What rules do you have at school?"。这一对分不清，考场白白丢分。
④ 完整体系全表：肯定 / 否定 / 疑问 / 搭配
很多同学只背了 must 一个词，其实它是一个完整家族，分"主观派"和"客观派"两列：
must 派（主观义务，无人称变化）
句式
结构
例句
KET 考查
肯定
主语 + must + 动词原形
You must be quiet in the library.
高频（规则/命令）
否定（禁止）
主语 + mustn't + 原形
You mustn't run near the pool.
高频（必考辨析）
疑问
Must + 主语 + 原形…?
Must I finish it today?
中频（听回答 Yes, you must. / No, you needn't.）
have to 派（客观不得不，有人称变化）
主语
肯定
否定（不必）
疑问
I / you / we / they
I have to get up early.
I don't have to wear a uniform on Fridays.
Do you have to work late?
he / she / it
She has to pass the exam.
He doesn't have to come tomorrow.
Does she have to drive?
过去（所有人称）
Yesterday I had to stay home.
We didn't have to wait long.
Did you have to pay?
三个必背细节
① must 后面永远跟动词原形，不能加 to：✗ must to study → ✓ must study。
② have to 有人称变化：第三人称单数是 has to，不是 have to；否定要用 do/does/did 帮忙。
③ must 没有过去式——过去的"不得不"一律用 had to。
高频职业搭配（KET Unit 11 话题直接用）
职业
日常义务（have to）
内在要求（must）
a nurse 护士
has to wear a uniform, work at night
must be patient with people
a pilot 飞行员
has to travel to many countries
must be healthy and careful
a teacher 老师
has to arrive at school early
must love children
a vet 兽医
has to look after sick animals
mustn't be afraid of dogs
语气强弱对比（写作/口语加分用）
说法
语气
例句
must
最强（说话人命令/强烈建议）
You must see this film!（你一定得看）
have to
中等（外部要求，较客观）
I have to finish this report by Friday.
should
较弱（建议，Unit 8 学过）
You should drink more water.
⑤ 场景全解：职业与校园里怎么用
场景
例句
记忆点
1 学校规则（主观命令）
We must be quiet in class. / We mustn't eat in the library.
规则用 must，禁令用 mustn't
2 职业要求（客观不得不）
A nurse has to work at night. / Pilots have to wear uniforms.
第三人称单数 has to
3 不必做（轻松）
You don't have to come if you're ill.
don't have to = 可以不来
4 过去不得不
Yesterday I had to walk home in the rain.
昨天的事用 had to
5 请求许可
Must I hand it in today? — No, you needn't.
Must I 的否定回答用 needn't
6 问对方日常
Do you have to take the bus to school?
Do you have to…? 口语高频
7 谈梦想门槛
If you want to be a doctor, you have to study for a long time.
want to be + have to 串职业话题
8 劝告与建议
You must see a doctor if you feel ill.（强烈建议）
must 表强烈建议时=一定得
考场一秒判断法看到空先问自己："这是禁止做，还是可以不做？" 禁止（做了会出事/违规）→ mustn't；可以不做（做不做都行）→ don't have to。90% 的完形空靠这一问就能选对。
⑥ 中国学生 5 大高频错误诊断
错误 1：must 后面加 to ✗ You must to study hard. → ✓ You must study hard. 口诀：must 是情态动词，后面直接跟动词原形，不加 to。
错误 2：mustn't 和 don't have to 搞反 ✗ You don't have to run near the pool.（想说"禁止跑"）→ ✓ You mustn't run near the pool. 危险=禁止=mustn't；无所谓=不必=don't have to。
错误 3：he/she 后用 have to ✗ She have to wear a uniform. → ✓ She has to wear a uniform. 第三人称单数，have 要变 has。
错误 4：过去式错用 must ✗ Yesterday I must finish my homework. → ✓ Yesterday I had to finish my homework. must 没有过去式，过去的"不得不"用 had to。
错误 5：否定疑问忘加 do/does ✗ Have you to wear a uniform? → ✓ Do you have to wear a uniform? have to 是实义动词，疑问否定都要请 do/does 帮忙。
⑦ KET 考点与真题演练
题型
怎么考
应对
Reading Part 5 完形
短文空里选 must / mustn't / don't have to
先判断"禁止"还是"不必"
Reading Part 1 告示
看图识告示："No smoking" = You mustn't smoke
告示=规则=must/mustn't
Writing 邮件/故事
写学校规则或职业要求
must 表规则，have to 表客观
Listening 对话
听 "Do you have to...?" 回答 Yes/No
抓 have to / don't have to
Speaking Part 1
"What rules do you have at school?"
must / have to / don't have to 各一句
真题风格演练（KET 出题方式）
真题风格 · Part 5完形：You ___ wear a uniform at our school — only on Mondays and Fridays.
A. mustn't B. don't have to C. have to
B。only on Mondays and Fridays = 不必每天穿 = don't have to。mustn't 是"禁止穿"，意思完全相反。
真题风格 · Part 1 告示图片是图书馆告示："Be quiet. No eating." 哪个句子对？
A. You must be quiet and mustn't eat. B. You don't have to be quiet. C. You can eat here.
A。图书馆要求安静（must be quiet）、禁止吃东西（mustn't eat）。
真题风格 · Speaking考官问：What do you have to do to be a doctor? 你怎么答？
参考：I have to study science at university for many years. I must also work hard and pass difficult exams.（have to 客观 + must 主观，两句都踩点）
⑧ 背诵内容：10 个必备句型 + 学校规则口语模板
每天背 3 句，3 天背完。边背边想：这句是"谁要求的"？
1. You must be quiet in the library. 图书馆里必须安静。
2. You mustn't run near the swimming pool. 泳池边禁止奔跑。
3. I have to get up at six on school days. 上学日我得六点起床。
4. My dad has to drive to the office every day. 我爸爸每天得开车去上班。
5. You don't have to wear a uniform on Fridays. 周五你不必穿校服。
6. She doesn't have to come if she's ill. 她病了就不必来。
7. Yesterday I had to stay at home. 昨天我不得不待在家里。
8.Must I finish it today? — No, you needn't. 我必须今天做完吗？——不必。
9.Do you have to take the bus to school? 你不得不坐公交上学吗？
10. If you want to be a nurse, you must study hard. 想当护士就必须努力学习。
学校规则口语模板（KET Speaking Part 1 直接套）
At my school, we must wear a uniform from Monday to Thursday. We mustn't use phones in class. We have to arrive before eight. But we don't have to wear a uniform on Fridays — we can wear our own clothes. On Sundays, I don't have to get up early. It's great!