stone可數(shù)嗎

　　例句：

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

　　不停的流水把這些石頭沖刷得很光滑。

　　2、The stone was dropped from a great height.

　　那塊石頭是從很高的地方掉落下來(lái)的。

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

　　一塊大石頭飛進(jìn)了窗戶。