burn的过去式和过去分词?

　　Turn the heat down or it'll burn.

　　把炉火开小一些，不然就烧焦了。

　　He's always had a burning ambition to start his own business.

　　他总是雄心勃勃地想自己创业。

　　A small fire was burning to take the chill off the room.

　　房间里生着小火炉驱寒。