语法点：被动语态 (Passive Voice)
被动语态用来强调"动作的承受者"，而不是"谁做的"。当我们不知道、不需要说或不想说动作的执行者时，就用被动。本课讲 Dan 的自行车失窃二十年后被警察找到，课文里自行车"被找到""被捡到""被送回""被偷走"，Dan"被要求""被告知"，大量使用被动语态。被动语态的基本形式是 be + 过去分词，be 动词随时态和主语变化；如果要说明执行者，用 by + 执行者。
结构
| 时态 | 结构 | 例句 |
|---|---|---|
| 一般过去时 | was / were + 过去分词 | The bicycle was picked up in a small village. |
| 一般现在时 | am / is / are + 过去分词 | The bicycle is kept at the station. |
| 现在进行时 | is / are being + 过去分词 | It is now being sent to his home by train. |
| 过去完成时 | had been + 过去分词 | His bicycle had been found. |
| 带 by | be + 过去分词 + by + 执行者 | He was wanted by the police. |
- 否定：was not sent；疑问：Was it sent…?
- 双宾语动词（ask / tell）的被动：He was asked to call at the station. He was told that…
课文中的例句
- [句 3] In the letter he was asked to call at the station. — was asked to do："被要求做某事"，执行者（警察）不必说出
- [句 4] Dan wondered why he was wanted by the police, but he went to the station yesterday and now he is not worried anymore. — was wanted by the police：用 by 点明执行者
- [句 5] At the station, he was told by a smiling policeman that his bicycle had been found. — 一句里两个被动：was told（过去时）和 had been found（过去完成时）
- [句 6] Five days ago, the policeman told him, the bicycle was picked up in a small village four hundred miles away. — 短语动词 pick up 的被动：was picked up
- [句 7] It is now being sent to his home by train. — 现在进行时被动 is being sent；by train 表示方式，不是执行者
- [句 10] It was stolen twenty years ago when Dan was a boy of fifteen! — was stolen：不知道谁偷的，自然用被动
补充例句
- The letter was sent to Dan last Tuesday. 这封信是上星期二寄给 Dan 的。
- The bicycle has been found by the police. 自行车已经被警察找到了。
- Dan is being asked a lot of questions at the station. Dan 正在警察局被问很多问题。
易错点
- ❌ The bicycle was pick up in a small village. → ✅ The bicycle was picked up in a small village. 被动语态必须用过去分词，不能用原形。
- ❌ It is now sending to his home by train. → ✅ It is now being sent to his home by train. 自行车是"被送"，正在进行的被动要用 is being + 过去分词。
- ❌ His bicycle was found by twenty years ago. → ✅ His bicycle was stolen twenty years ago. by 后面只能接执行者，时间状语前不加 by。
- ❌ He was told by a policeman that his bicycle was found. → ✅ He was told by a policeman that his bicycle had been found. "被找到"发生在"被告知"之前，要用过去完成时的被动。