用on
on fire 着火:
The ware house is on fire.仓库着火了。
1、 on fire：这个词组的意思是“着火起火”
例句：
Look， the car is on fire!看，车着火了！
Protesters set cars on fire and burned a building.抗议者们焚烧汽车，烧毁了一栋建筑。
This building is on fire， you must evacuate immediately.这座楼着火了，大家必须立即疏散。
2、 on the fire：这个词组的意思是“在考虑中在审议中”。
例句：Who will attend the meeting is on the fire.参加会议的人选还未决定。
The time when we will have a meeting is on the fire.
我们什么时候开会还在考虑之中。
Where we will have the party is on the fire.我们在什么地方聚会还未决定。
