旁听者

例句：

1. 1. He was a spectator at the football match.
   他在足球比赛中当了一名观众。
2. 2. The teacher asked all the students to be spectators during the exam.
   老师要求所有学生在考试期间充当观众。
3. 3. She was an observer of the new policy changes in the city.
   她观察了城市新的政策变化。