tracing milling

例句：

1. 1. The detective was tracing the movements of a suspect.
   侦探正在追踪嫌疑人的行踪。
2. 2. The team is tracing the origins of the virus.
   团队正在追踪病毒的起源。
3. 3. She traced her steps back to the spot where she had left her keys.
   她追溯自己的足迹，回到了她留下钥匙的地方。