1) Give me a can, please.

我买一筒。
2) I need to buy a can of tooth paste.

我需要买一筒了。
3) I bought a raincoat.

我买了一件雨衣。
4) I want to buy a raincoat.

我想买一件雨衣。
5) I'll buy you another one.

我再买一个给你。
6) That's all I could afford.

我只买得起一朵。
参考词条