clast

例句：

1. 1.The beach is covered with smooth, white cobbles.
   海滩上铺满了光滑的白色卵石。
2. 2. She picked up a few pebbles from the ground.
   她从地上捡起了几块卵石。
3. 3. The river flows through a landscape of smooth cobblestones.
   河流穿过一片平滑的卵石景观。