sand可數嗎?

　　例句

　　1.The sand on the floor scrunched under our feet.

　　地板上的沙子在我們腳下嘎吱作響。

　　2.The sand martin is a brown bird with white underneath.

　　崖沙燕是一種褐羽白腹的鳥。

　　3.They all walked barefoot across the damp sand to the water's edge.

　　他們全都光著腳走過潮濕的沙地來到水邊。

　　4.The ship has come to rest on the fine sand.

　　這艘船停靠在細沙灘上。