定义 / 说明
英语谈过去能力时有不同形式，选择取决于语义。could 通常表示一段时期内的一般能力（如小时候会某技能）。was able to 和 managed to 常用于“某个具体场景下成功做到某事”。这个区别很重要：单次成功事件用 was able to/managed to 更自然。核心是区分“一般能力”与“具体成就”。
关键规则
- could：一般过去能力：I could read at four.
- was/were able to：某次具体成功：We were able to get tickets.
- managed to：强调“有难度但最终成功”。
- 否定中 couldn't 对一般能力和具体失败都常自然。
- 不要在“某次已完成成功”场景中过度使用 could。
例句
- I could swim when I was five. - 我五岁时就会游泳。
- We were able to find the house in the dark. - 我们在黑暗中还是找到了那栋房子。
- She managed to fix the printer. - 她设法修好了打印机。
- He couldn't open the door. - 他打不开门。
- After three hours, they managed to solve the problem. - 三小时后他们终于解决了问题。
常见错误
- ❌ Yesterday I could fix the laptop after two hours. -> ✅ Yesterday I managed to fix the laptop after two hours.
- ❌ We were able finding the station. -> ✅ We were able to find the station.
- ❌ I could to swim at five. -> ✅ I could swim at five.