说出义务和能力
能准确地说出我必须做什么、不必做什么，以及我做成了什么。
标注的核心时长。核心模块中有两项未标注时长，因此实际课时比总和更长。
语法
16 分钟本课把 A2 里没有讲完的两个话题合在一起。第一个是能力和成功：can（A1 第20课）的形式太少。第二个是规则：在 must、have to（A2 第10课）和 should（A2 第11课）之外，再加上“按规定应该” “允许”和“不必”。
be able to——任何时态里的能力。 can 只有两个形式：can 和 could。它没有将来时、没有完成时，也不能放在另一个动词后面——这些地方要用 be able to。
| 将来 | I'll be able to swim by the summer. |
| 完成时 | I haven't been able to sleep this week. |
| 在另一个动词后面 | I'd like to be able to speak French. |
| 在情态动词后面 | You might be able to get a ticket online. |
| 过去 | I wasn't able to come yesterday. |
现在时一般用 can：I can swim 比 I'm able to swim 听起来自然。
会，还是做成了？ 说过去的事时，英语要区分两种情况，汉语的“能”却常常把它们都包括在内。 could 表示一般的能力，在一段时间里一直都会：I could read when I was four. 某一次具体的成功用 was able to 或 managed to。managed to 强调：很难，但是做成了。
| I could swim when I was six. | 六岁时就会游泳。 |
| The water was cold, but I managed to swim to the boat. | 那一次成功游到了船边。 |
否定句里没有这种区别，couldn't 什么时候都可以用：I couldn't find my keys this morning. 和感知动词 see、hear 连用时，could 说某一次的事也没有问题： I could hear music next door.
在肯定句里，was able to 和 managed to 差不多，但 managed to 直接点出了困难和努力。所以它常常和 but、in the end 一起出现：It took three hours, but in the end we managed to fix it. 如果没有什么困难，一般就直接用一般过去时： I finished the report on Friday.
be supposed to——按规定应该，按约定应该。 义务既不是来自说话人，也不是来自法律，而是来自规则、约定或者别人的期待。 You're supposed to take your shoes off in the house.——习惯如此。 I'm supposed to be at work at nine.——约好了。这个形式里常常听得出，实际情况并非如此：I'm supposed to be working, but I'm watching football. 用过去时，几乎总是“本来应该，但是没有发生”： The train was supposed to arrive at six.——结果七点才到。 not supposed to 是按规定的温和禁止，比 mustn't 温和：You're not supposed to park here. 这里的 supposed 是形容词，所以总是需要 be：I'm supposed to， Were we supposed to…?
和 have to 比较一下。I have to be at work at nine——我别无选择：迟到就会有麻烦。 I'm supposed to be at work at nine——规定是这样，但听起来这条规定是可以违反的，说不定我就会违反。所以解释事情为什么没有按计划进行时，be supposed to 很合适。
be allowed to——可以，被允许。 许可来自别人：规则、法律、父母、上司。allowed 是 allow“允许”的第三种形式，所以从结构上看这是被动语态，你在告示 Pets aren't allowed（A2 第19课）里已经见过：不是“我允许”，而是“我被允许”。be 随人称和时态变化，allowed to + 动词保持不变。
| 肯定 | We're allowed to use dictionaries in the exam. |
| 否定 | You aren't allowed to smoke on the train. |
| 疑问 | Are we allowed to take photos? |
| 过去 | I wasn't allowed to stay out late as a child. |
| 将来 | Next year students will be allowed to use phones in class. |
can 还是 be allowed to？ 现在时说许可，常常直接用 can：You can park here after six. be allowed to 强调许可来自规则或者别人，所以通报规定或者询问规定时，它听起来更准确：Are we allowed to bring food into the museum? 将来时和完成时里 can 没有形式，必须用 be allowed to——和 be able to 一样：Will we be allowed to park here? 说过去时，界线和 could、managed to 一样： could 是一般的、长期的许可（As a child I could watch TV until nine），was allowed to 是某一次的许可（Yesterday we were allowed to leave early）。
supposed to 还是 allowed to？ 两者都和规则有关，说的却是不同的事。supposed to—— 应该做什么，allowed to——可以做什么。在否定句里，区别在于语气的强弱：
| You're supposed to wear a helmet. | 按规定应该：这是义务 |
| You're allowed to bring one bag. | 可以这样：这是许可 |
| You're not supposed to park here. | 按规定不该——说得委婉，很多人还是照样停车 |
| You're not allowed to park here. | 禁止——直截了当，没有余地 |
don't need to——没有必要。 它和 don't have to（A2 第10课）一样：可以不做。这里的 need 是带 to 的普通动词，所以否定、疑问和过去时都用 do 构成： You don't need to come tomorrow. Does she need to bring anything? We didn't need to wait. 不要把它和表示“不许”的 mustn't、not allowed to 混淆：You don't need to come—— 可以不来；You aren't allowed to come——不许来。
用一个例子看整个等级：
| I must finish today. | 我自己这样决定 |
| I have to finish today. | 情况要求如此 |
| I'm supposed to finish today. | 约好了——可是来得及吗？ |
| I should finish today. | 这样做才对 |
| I'm allowed to finish tomorrow. | 允许我明天再完成 |
| I don't need to finish today. | 今天可以不完成 |
| I mustn't forget the figures. | 不许忘记 |
不能这样说。 ✗ We didn't need come so early → ✓ We didn't need to come so early。 didn't need 是普通动词，后面要加 to。
自我检测。 “很难，但我还是赶上了火车”用 could 还是 managed to？ The film was supposed to start at eight 是什么意思？“上班时我们不许用手机”英语怎么说？
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中文母语者的常见错误
已针对你的语言编写两个情态动词连用。
✗ I will can swim
✓ I'll be able to swim
。汉语说将来的能力， “将”“就”可以和“能”连着用（“我将能……”“到夏天我就能……”），于是拼成了 will can。可是英语里两个情态动词不能连用，第二个位置要用 be able to。
用 could 说某一次做成了。
✗ The exam was hard, but I could pass it
✓ The exam was hard, but I managed to pass it / I was able to pass it
。“能”记作 can，它的过去就是 could，于是“那次我终于能通过考试了”也译成了 could。可是肯定句里的 could 表示一般的能力，不是那一次的成功。
漏掉 be 或者 -d。
✗ I supposed to be there at nine → ✓ I'm supposed to be there at nine； ✗ We are not allow to smoke → ✓ We aren't allowed to smoke。“我应该九点到”里的“应该”像普通动词，前面没有“是”，于是 be 就丢了。汉语动词没有词尾，-d 也容易丢：✗ suppose to、 ✗ allow to。可是 supposed 在这里是形容词，allowed 是被动语态的一部分：两者都要有 be，也都要有 -d。
用 Here 或 It 作主语。
✗ Here isn't allowed to smoke / ✗ It isn't allowed to smoke here → ✓ You aren't allowed to smoke here。“这里不允许抽烟”没有说谁不被允许，于是“这里”成了主语，或者换上一个 It。可是 be allowed to 的主语是被允许或被禁止的人：You aren't allowed、 Passengers aren't allowed。想说被禁止的东西本身，就让它作主语：Pets aren't allowed；告示牌上干脆写 No smoking。
发音
4 分钟supposed to 读作 /səˈpəʊs tə/： -d 和 t 合成一个 /t/。第一个音节不重读——/sə/，重音在第二个音节：su-POSED。
able 读作 /ˈeɪbl/， 重读的 /eɪ/，和 table 里一样。be able to 要一口气完整地说出来： /bi ˈeɪbl tə/；to 是弱读的 /tə/。
managed to 读作 /ˈmænɪdʒ tə/： /t/ 前面的 /d/ 几乎听不见。allowed to /əˈlaʊd tə/ 也一样：/d/ 和 /t/ 合在一起，和 supposed to 里一样。allowed 听起来就像 loud 前面加一个弱读的 /ə/——和 aloud“出声地”读音完全相同。
课文
5 分钟Hi Claire,
I'm afraid the report isn't ready yet. I was supposed to send it to you yesterday, but I wasn't able to finish it. At four o'clock my laptop suddenly stopped working, and nobody in IT could fix it the same day.
The good news is that I managed to save most of the file — I only lost the last two pages. Sam has lent me his old laptop, and I'm allowed to keep it until Friday, so I'll be able to finish everything this morning. You'll have it by twelve.
You don't need to move the meeting with the client. The figures are all correct — I checked them twice on Monday. But I'm supposed to show the report to Mark first, and he's working from home today. Do you need to see it too, or can I send it straight to him?
One more thing: we're not supposed to leave laptops in the office overnight, but mine stayed there because it wasn't working. I hope that's all right.
Sorry again, Ben
练习
30 分钟1. 填空。
- I swim when I was five.（当时就会）
- Don't worry, you drive by the summer.（将来）
- I haven't sleep well since we moved
- She speak three languages.（现在）
- I'd like to play the piano
- I'm sorry, I come to your party last Saturday.（没能来）
- If you call the hotel, you might get a cheaper room
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2. 选择。
- My grandmother read without glasses until she was ninety
- The traffic was terrible, but we get to the airport on time
- The door was locked, but the firefighters get in through the window
- When I was young, I run ten kilometres easily
- The exam was really difficult, but she pass it
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3. 用 be able to 改写
- I can drive. (next year)
- She can't come to the meeting. (yesterday)
- I can't sleep. (this week ——完成时)
- We can visit you. (in the summer)
- He can't find a job. (since March ——完成时)
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4. 用 be supposed to 改写。
- The rule is: take your shoes off at the door.
- We agreed to meet at six, but he isn't here.
- The timetable says the train arrives at five, but it's late.
- You can't park here — it's against the rules.
- I should be studying now, but I'm watching TV.
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5. 用 be allowed to 或 don't need to 改写。
- It isn't necessary to bring food — there's a café.
- It wasn't necessary for us to wait — the doctor saw us at once.
- The rules say you can't take photos in the museum.
- As a child, I couldn't stay out after nine — my parents said no.
- From next year students can use phones in class.（将来）
- Can we bring our own drinks into the cinema?（问一问规定）
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6. 改错。
- I will can drive next year.
- The exam was hard, but I could pass it.
- I supposed to be at work at nine.
- It isn't allowed to take photos here.
- We didn't need come so early.
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7. 用完整的句子回答
——说说你自己。下面的答案是范例。 1) What would you like to be able to do? 2) What difficult thing did you manage to do last month? 3) What are you supposed to do every day that you don't always do? 4) What weren't you allowed to do as a child?
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8. 译成英语。
1) 再过一个月，我的英语就能说得更流利了。 2) 当时很难，但我们还是赶上了最后一班火车。 3) 火车本来应该六点到。 4) 你明天不用来。 5) 按规定这里不该抽烟。
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小结
本课已学：各种时态中以及其他动词后面的 be able to，could 和 managed to、was able to 的区别；规则——现在时和过去时的 be supposed to，be allowed to 与 can、与 not supposed to 的比较，don't need to 和 mustn't 的区别，义务的整个等级。下一课——第12课：复习第7–11课。
核心内容结束
完成练习后即视为课程结束。此后的内容均为可选。
可选
词卡词汇
14 词- be able to /bi ˈeɪbl tə/ 能，能够
- manage to /ˈmænɪdʒ tə/ 设法做到，做成
- be supposed to /bi səˈpəʊs tə/ 应该（按规定或约定）
- be allowed to /bi əˈlaʊd tə/ 被允许，可以（经过许可）
- laptop /ˈlæptɒp/ 笔记本电脑
- fix /fɪks/ 修理，修好
- save /seɪv/ 保存
- file /faɪl/ 文件
- figures /ˈfɪɡəz/ 数字，数据
- straight /streɪt/ 直接，马上
- overnight /ˌəʊvəˈnaɪt/ 过夜，整夜
- glasses /ˈɡlɑːsɪz/ 眼镜
- firefighter /ˈfaɪəfaɪtə/ 消防员
- locked /lɒkt/ 锁着的
写作
写五六句话，说说没有按计划进行的一天：你本来应该做什么，什么没能做成，什么最终还是做成了，现在又有什么可以不做了。
范例： Yesterday I was supposed to meet a client at ten, but I wasn't able to get there on time. There was an accident on the motorway, and the traffic didn't move for an hour. I managed to call the client from the car, and she was very kind about it. In the end we had the meeting online. So now I don't need to drive to her office next week. I hope I'll be able to meet her in person next month.
检查清单：will 后面和完成时里用的是 be able to，而不是 can 吧？说某一次的成功用的是 managed to 或 was able to，而不是 could 吧？supposed to 和 allowed to 前面有 be 吗？ “可以不做”用的是 don't need to，而不是 mustn't 吧？