定义 / 说明
完成时被动语态把“完成”与“被动焦点”结合起来。它用于表示“某人/某物已经被做了某事”，常与另一时间点形成先后关系。主要形式是 has/have been + past participle 和 had been + past participle。在正式写作、报告和结果说明中很常见，因为它把注意力放在结果和受事上，而非执行者。
关键规则
- 现在完成时被动：has/have been + past participle。
- 过去完成时被动：had been + past participle。
- 当动作已完成且受事仍是焦点时使用。
- 只有执行者重要时才用 by 引出。
- 区分 has been doing（主动进行）与 has been done（被动完成）。
例句
- The work has been completed. - 工作已经完成。
- The email had been sent before lunch. - 午饭前邮件就已发出。
- The tickets have already been sold. - 票已经卖完了。
- The problem had been solved by the time I arrived. - 我到时问题已经解决。
- A new system has been introduced. - 一个新系统已被引入。
常见错误
- ❌ The work has completed. -> ✅ The work has been completed.
- ❌ The email had been send before lunch. -> ✅ The email had been sent before lunch.
- ❌ The tickets have been sold already yesterday. -> ✅ The tickets were sold yesterday. / ✅ The tickets have already been sold.