stone可数吗

　　例句：

　　1、The stones have been worn smooth by the constant flow of water.

　　不停的流水把这些石头冲刷得很光滑。

　　2、The stone was dropped from a great height.

　　那块石头是从很高的地方掉落下来的。

　　3、A large stone came flying in through the window.

　　一块大石头飞进了窗户。