什么时候用被动语态？口诀：不知动作执行者，强调动作承受者；动作执行者用 by 引出。
顺口溜记忆
- 不知谁做用被动，强调动作承受者
- 执行者用 by 引出，放在句末别忘记
- 感官使役动词后，主动省 to 被动还原
- 不及物动词无被动，happen、appear 记心间
要点讲解
- 不知道或没必要说明动作执行者时用被动：My bike was stolen. 我的自行车被偷了。
- 强调动作的承受者：The Great Wall is known all over the world. 长城举世闻名。
- by + 执行者：The cake was made by my mother. 蛋糕是我妈妈做的。
- 感官动词/使役动词主动语态省略 to，被动语态要还原：I saw him go out. → He was seen to go out.
- get + 过去分词也可表被动：He got hurt. 他受伤了。
例句解析
- The window was broken by the boy. 窗户被那个男孩打破了。
- English is widely used in the world. 英语在世界上被广泛使用。
- He was seen to enter the room. 有人看见他进了房间。
- The problem must be solved at once. 这个问题必须立刻解决。
易错提醒
- 主动变被动时，宾语变主语，动词变 be + 过去分词，主语变 by 短语（可省略）；时态要保持一致。