My little sister can read simple English stories. 我妹妹会读简单英文故事。
He can fix basic computer problems by himself. 他能自己解决基础电脑问题。
Can you explain this question in Chinese? 你能用中文解释这道题吗？
语用提示：能力型 can 常带“自信、鼓励、认可”。 鼓励Teacher: You can do it step by step. 认可Parent: You can handle this challenge now.
2) can 表许可（可以，被允许）
规则：向别人请求允许或说明规则允许，用 can。
Can I borrow your ruler for a minute? 我可以借你的尺子用一分钟吗？
You can use your dictionary during group work. 小组活动时你可以用词典。
Students can leave after they finish the quiz. 学生做完小测后可以离开。
语用提示：许可型 can 语气中性直接；换成 Could I...? 会更礼貌、更克制。 直接请求Can I open the window? 礼貌请求Could I open the window, please?
3) mustn't vs don't have to（绝对禁止 vs 不必）
规则：mustn't = 不准做；don't have to = 没必要做（可做可不做）。
You mustn't cross the road when the light is red. 红灯时你绝对不能过马路。
You don't have to bring lunch tomorrow; the school provides it. 明天你不必带午饭，学校会提供。
We mustn't talk loudly in the library. 我们在图书馆绝对不准大声说话。
mustn't：You mustn't touch this switch.（碰了会有危险）
don't have to：You don't have to come so early.（来不来都可以）
语用提示：mustn't 带“警告、严厉、边界感”；don't have to 带“放松、减压、给选择”。 规则提醒You mustn't enter this room without permission. 减压安抚You don't have to finish all of it tonight.
③ 综合层：义务来源与句型变化
目标：能根据“义务来源”和“句型变化”做出准确选择
1) must vs have to（主观要求 vs 客观要求）
规则：must 多表示说话人主观“我必须”；have to 多表示规则/现实“不得不”。
I must finish this report tonight because I promised my team. 我今晚必须完成报告，因为我答应了团队。（主观）
We have to wear uniforms on Mondays. 我们周一必须穿校服。（校规）
I don't like it, but I have to get up at 5:30 for the bus. 我不喜欢，但为了校车我不得不5:30起床。（客观现实）
语用提示：must 更像“我内心下决心”；have to 更像“现实要求如此”。 坚定决心I must change my habits this month. 无奈客观I have to cancel the trip because of the rain.
2) Must I ...? 的否定回答
规则：问句 Must I ...? 否定回答通常是 No, you don't have to.（表示不必）。
Must I hand it in today? — No, you don't have to. 我今天必须交吗？— 不必。
Must we finish all ten questions now? — No, you don't have to. 我们现在必须做完十题吗？— 不必。
语用提示：这个回答常用于“缓和压力”，语义是“可以不现在做”，不是“禁止你做”。 缓和语气No, you don't have to. Take your time.
3) have to 的疑问句与否定句
规则：一般现在时用 do/does + 主语 + have to ...?；否定用 don't / doesn't have to。
Do you have to stay at school after class? 你课后必须留校吗？
She doesn't have to take the bus; her dad drives her. 她不必坐公交，她爸爸接送。
Do we have to submit a doctor's note? 我们必须提交医生证明吗？
语用提示：Do we have to...? 常含“确认规则/表达顾虑”；don't have to 表示“不必如此”。 确认规则Do we have to wear ties every day? 松一口气Great, we don't have to pay today.
4) 课堂高频交际模板（口语与书面都实用）
规则：把情态词放进“解释原因 + 请求通融”模板，表达更完整。
I have to leave early because my mom is waiting outside. 我得提前离开，因为我妈妈在外面等我。
Could I hand it in tomorrow? I must check the data again tonight. 我可以明天交吗？我今晚必须再核对数据。
Do we have to finish all parts today, or can we do Part B tomorrow? 我们今天必须全部做完吗，还是 B 部分可以明天做？
④ 提升层：推断、过去义务与易错辨析
目标：掌握常见易错点：推测语气、过去义务、语义误判
1) must / can't 表推测（不是禁止）
规则：有证据的肯定推测用 must；否定推测用 can't。注意这不是“禁止”。
The lights are on. Mr. Brown must be in his office. 灯亮着，布朗老师一定在办公室。（推测）
He can't be at home now; I just saw him at the station. 他现在不可能在家，我刚在车站见过他。
This must be your notebook; your name is on it. 这一定是你的笔记本，上面有你的名字。
语用提示：推测 must 表示把握很高；can't 表示基于证据的否定判断。 笃定She must be the team leader. 强否定He can't be serious.
2) must 没有过去式：过去“不得不”用 had to
规则：出现 yesterday / last night / in 2024 等过去时间，优先考虑 had to。
My bike was broken, so I had to walk home yesterday. 昨天我的自行车坏了，所以我不得不走回家。
We had to cancel the trip because of the storm. 因为暴风雨，我们不得不取消行程。
She had to stay up late to finish the project. 她不得不熬夜完成项目。
语用提示：had to 常用于回顾过去的客观压力或必要安排，叙事感比现在时更强。 回顾无奈I had to miss the party because I was ill.
3) 交际语气：礼貌请求可用 Could I...?
规则：常见 can I...；真实口语中更礼貌可用 could I...（许可语气更委婉）。
Could I leave five minutes early for my doctor's appointment? 我可以提前五分钟离开去看医生吗？
Could I ask one more question before we finish? 结束前我可以再问一个问题吗？
语用提示：Could I...? 比 Can I...? 更委婉，常用于正式场景、求人帮忙或需要照顾对方感受时。 更有分寸Could I speak to you for a moment?
4) 高阶语感：mustn't 与 can't 的差别
规则：mustn't 常是规则“禁止做”；can't 常是“不能/不可能”。
You mustn't enter this lab without a teacher. 没有老师带领，你不准进入这个实验室。（规则禁止）
This answer can't be right because the units don't match. 这个答案不可能对，因为单位都不匹配。（逻辑否定）
He can't finish it in two minutes; it's too complex. 他两分钟内不可能完成，这太复杂了。（能力/现实不可能）
语用提示：mustn't 强调规则禁止；can't 常表示事实不可能或能力做不到，语义重心不同。 规则提醒You mustn't copy answers in the exam.
⑤ 实战微练：即时判断
说明：先独立填空；屏幕可展开参考答案。打印版不印答案。建议口头解释「为什么不是别的选项」。
1) The sign says “No Photos”. Visitors ______ take photos here.
2) Must I finish this today? — No, you ______.
3) My bike broke down, so I ______ walk to school yesterday.
4) Whose bag is this? It ______ be Lucy's. Her name is on it.
5) ______ I use your phone for one minute?
6) He ______ be in class now. I just saw him at the hospital.
参考答案（教师讲评用，打印时不显示）
mustn't（绝对禁止）
don't have to（不必）
had to（过去“不得不”）
must（肯定推测）
Can / Could（请求许可）
can't（否定推测）
自检清单：
看到“规则、标志、危险”先想：是不是 mustn't。
看到“可做可不做”先想：是不是 don't have to。
看到过去时间词先检查：是否要用 had to。
看到证据推断先区分：must be / can't be。
⑥ 总复盘：成对辨析
目标：把全讲最易混点做最后一次“成对辨析”与“快测复核”。
mustn't vs don't have to You mustn't park here. 你不准在这停车（禁止）。 You don't have to park here. 你不必在这停车（可选）。
must vs have to I must call my grandma tonight. 我今晚必须给奶奶打电话（主观）。 I have to wear a uniform at school. 我在学校必须穿校服（客观）。
must be vs can't be The lights are on. He must be at home. 灯亮着，他一定在家（肯定推测）。 He can't be at home. I saw him outside. 他不可能在家，我刚在外面看见他。
have to vs had to I have to finish it today. 我今天不得不完成（现在）。 I had to finish it yesterday. 我昨天不得不完成（过去）。
收束快测（再核对 4 题）：
The sign says “Danger”. You ______ swim here. [mustn't]
Must I finish this now? — No, you ______. [don't have to]
My bike was broken, so I ______ walk home yesterday. [had to]
That man ______ be our teacher; our teacher is abroad. [can't]
核心结论：先判断“语义”（能力/许可/义务/禁止/推测），再选“形式”。
出现过去时间词时优先检查 had to；危险禁令优先检查 mustn't。
易错提醒：mustn't（绝对禁止）≠ don't have to（不必）。
推测题中「他不可能是……」常用 can't be，不是 mustn't be。
背诵口诀 · 一页收束
can 能力许可，must 主观义务；have to 客观不得不，过去 had to；
mustn't 绝对禁止，don't have to 不必做；
must be 有把握，can't be 不可能；情态后动词原形记牢。