綿羊是不是可數名詞?

　　例句：

　　They kept a small flock of sheep.

　　他們養了一小群綿羊。

　　The field had been grazed by sheep.

　　這塊地羊已經啃過了。

　　This wool comes from goats, not sheep.

　　這種羊毛是山羊毛，不是綿羊毛。