mustn't ≠ don't have tomustn't = 千万不能（禁止）；don't have to = 不必（可做可不做）。差一个词，意思相反。
从 KET 到 PET 的进阶提醒KET（A2）要求"能认出、能填对"；PET（B1）要求"会用、会说、会写"。同一个知识点，A2 只考单选，B1 还要你在 email 和口语里主动输出。所以这一课别停留在"看懂"，一定要把第 ⑧ΣA; 部分的句子大声说出来、写一遍。评分也更严：语法错一个、漏一个要点，写作分就往下掉一档。
④ 三档建议句型表
委婉建议
句型
例句
You should + 原形
You should get more sleep.
You ought to + 原形
You ought to drink more water.
Why don't you + 原形?
Why don't you take a day off?
If I were you, I would...
If I were you, I would rest.
红线 / 留余地
句型
意思
例句
mustn't + 原形
禁止
You mustn't eat sweets before bed.
don't have to + 原形
不必
You don't have to give up fast food completely.
can / It's OK to
可以/没关系
You can have a cake sometimes.
情态动词后永远原形should to go / mustn't eating 都错——should go / mustn't eat。
⑤ 五类建议场景（配图记忆）
场景
例句
语气
1 提温和建议
You should go to bed earlier.
should
2 更委婉
If I were you, I would see a doctor.
虚拟建议
3 给红线
You mustn't drink and drive.
禁止
4 留余地
You don't have to stop sugar completely.
不必
5 提议一起
Why don't we go for a walk?
提议
If I were you 的 were虚拟语气里所有人称都用 were：If I were you（口语可用 was，写作推荐 were）。
⑥ 中国学生 5 大高频错误诊断
错误 1：mustn't / don't have to 混 ✗ You mustn't come if you're busy.（想说不必）→ ✓ You don't have to come. 忙就别来 = 不必，不是禁止。
错误 2：情态后加 to ✗ You should to rest. → ✓ You should rest. 情态动词后原形。
错误 3：If I was you（写作） 写作推荐 If I were you, I would...。 虚拟语气用 were。
错误 4：建议太极端 ✗ You must stop eating all sugar. → ✓ You should eat less sugar.（更有分寸）。 好建议不极端。
错误 5：Why don't you 后加 to ✗ Why don't you to rest? → ✓ Why don't you rest? 后接原形。
⑦ PET 考点与真题演练
题型
怎么考
应对
Reading Part 5 完形
挖 mustn't / don't have to 空
看是禁令还是可做可不做
Writing Part 6 email
给朋友健康/生活建议
三档语气各一句
Listening Part 1
听医生医嘱
抓 should / mustn't
Speaking Part 4
谈健康规定/给建议
If I were you, I would...
真题风格演练（PET 出题方式）
真题风格 · PET Reading Part 5 完形You (1) ______ eat more vegetables, but you (2) ______ stop eating chocolate completely — you (3) ______ have one bar a week.
(1) should；(2) don't have to（不必全戒）；(3) can（可以）。
真题风格 · PET 选词You ______ smoke in the hospital. (mustn't / don't have to)
mustn't。医院禁烟 = 禁止。
真题风格 · PET Writing Part 6 email写 2 句给熬夜朋友的健康建议。
参考：You should go to bed earlier. If I were you, I would stop playing games an hour before bed. You don't have to give them up completely!
考场提分提醒完形里看到"禁令/危险"选 mustn't；看到"可做可不做"选 don't have to。写作建议 email 主动用三档：should（建议）+ mustn't（红线）+ don't have to（余地），立刻显得有分寸、像 B1。
PET（B1）四部分速查
部分
时间
题量
与本课关系
Reading & Writing
1 小时 45 分
阅读 5 部分 + 写作 2 题
本课语法/词汇是 Part 5 完形与 Part 6 email 的得分点
Listening
约 12 分钟
4 部分，听两遍
抓本课信号词即可定位答案
Speaking
10-12 分钟
4 部分（含搭档）
本课背诵句直接用于 Part 2 独白与 Part 3 讨论
写作 Part 6 email 要求约 100 词、必须覆盖题目三个要点；口语 Part 2 个人独白约 1-2 分钟，Part 3 要和搭档互动（附和、提问、商量），不能各说各话。
3. If I ___ you, I would see a doctor. 如果我是你，我会去看医生。
4. You ___ eat sweets before bed. 你睡前不能吃糖。
5. You don't ___ to give up fast food. 你不必完全戒快餐。
6. You ___ have a cake sometimes. 你偶尔可以吃块蛋糕。
7. You ___ drink more water. 你该多喝水。
8. Don't ___ and drive. 别酒后驾车。
9. You ought to ___ more exercise. 你该多锻炼。
10. Why ___ we go for a walk? 我们为什么不出去走走？
给朋友健康建议 email（PET Writing Part 6 直接套）
Hi Sam, thanks for your email! I'm sorry you're tired. You should go to bed earlier and drink more water. If I were you, I would stop playing computer games an hour before bed. But you don't have to give them up completely — just one hour less! And remember, you mustn't drink coffee at night. Write soon!
ΣA; 口语练习：说出来才算会
PET Writing Part 1 email 万能开头/结尾（约 100 词三段式）开头：Hi Tom, thanks for your email — it was great to hear from you! 中间：题目给的三个要点，每个一句，用上本课语法/词汇。结尾：Write soon and tell me your news! Best wishes, Leo. 记住：三个要点缺一不可，否则扣分。
练习 A · 跟读（2 分钟）
跟着上面背诵卡读 3 遍：第一遍慢读看发音，第二遍正常速度，第三遍不看文字凭记忆说。
PET Speaking Part 2 个人独白万能开头/结尾（1-2 分钟）开头：I'd like to talk about... / The thing I want to tell you about is...；中间用 First of all... Also... But I think... 串两三个点；结尾：So, that's why I like it. Thank you for listening. 记住：别只说一句，要给例子、给理由，撑满 1 分钟。
练习 B · 自我对话（3 分钟）
Q: What should I do? → A: You should rest.
Q: Can I eat pizza? → A: Yes, you can — sometimes.
Q: Must I stop sugar? → A: No, you don't have to stop completely.
练习 C · 挑战（2 分钟）
不用稿子，用 should / mustn't / don't have to 各给一条健康建议。
口语评分自查说完后对 3 条：① 情态后接原形了吗？② 禁止用 mustn't、不必用 don't have to 了吗？③ 语气有分寸不极端吗？
考场示范对话（读熟就能套）
Examiner: A friend often feels tired. What advice would you give? You: I think they should sleep eight hours. They mustn't drink coffee at night, but they don't have to give up tea.