她无意中听到同事们在讨论项目。

She accidentally ___overheard her coworkers discussing the project.

他在火车上无意中听到两个陌生人之间的对话。

He ___overheard a conversation between two strangers on the train.

未经允许偷听私人对话是不礼貌的。

It's rude to ___overhear private conversations without permission.