追踪者

例句：

1. 1.The police are using a tracker to find the missing child.
   警方正在使用追踪器来寻找失踪的孩子。
2. 2. They used a tracker to follow the trail of the stolen car.
   他们使用了追踪器来追踪被盗汽车的踪迹。
3. 3. The tracker device was designed to help farmers monitor their crops.
   这种追踪设备旨在帮助农民监控他们的农作物。