ice可数还是不可数用法是什么意思

　　It was difficult to maintain a secure foothold on the ice.

　　在冰上不容易站稳脚。

　　He gave a longing look at the ice cream.

　　他看了看那冰激凌，显出很想吃的样子。

　　I had another helping of ice cream out of pure greed.

　　我纯粹是因为嘴馋贪吃，又吃了一份冰激凌。

　　The kids still weren't full, so I gave them an ice cream each.

　　孩子们还没有吃饱，所以我给他们每人一份冰激凌。

　　The car skidded on the ice and went straight into the wall.

　　汽车在冰上打滑，径直撞到了墙上。