trigger action

例句：

1. 1.The sudden noise triggered an alarm in the room.
   突然的噪音触发了房间里的警报。
2. 2.She acted as a trigger for the revolution.
   她作为革命的触发者。
3. 3.The gun was used as a trigger to start the machine.
   枪被用作启动机器的触发器。