track cross level

例句：

1. 1. The train tracks are visible from the window.
   从窗户可以看到火车轨道。
2. 2. They followed the tracks to find their lost dog.
   他们沿着轨道找到了他们的丢失的狗。
3. 3. The hikers followed the tracks to reach the summit.
   徒步旅行者沿着轨道到达山顶。