riblet

例句：

1. 1. The river flows over smooth pebbles and through a babbling brook.
   河流流过平滑的卵石和一条潺潺的小溪。
2. 2.The path is lined with smooth pebbles that make it easy to walk.
   这条小路两旁铺着光滑的卵石，走起来很轻松。
3. 3. The rocks in the park are all smooth pebbles that have been polished by the wind and rain.
   公园里的岩石都是经过风吹雨打的光滑卵石。