stock rails per kilometer of track

例句：

1. 1. The train isrunning on the new railway line.
   火车正在新铁路线上运行。
2. 2. Theengineer inspected the stock rails beforestarting the work.
   工程师在开始工作前检查了轨道枕木。
3. 3. Theconstruction crew was busy installingthe stock rails for thenew bridge.
   施工队忙于安装新的桥梁的轨道枕木。