layer of gravel

例句：

1. 1. The path was coveredin a layer of fresh snow.
   这条小径覆盖着一层新鲜的雪。
2. 2. The builders had to remove the layer of dirtbefore starting work.
   建筑工人在开始工作前必须清除这层泥土。
3. 3. The carwas parked on top of a layerof loose sand.
   汽车停在了一层松散的沙子上。