The fireman started to put out the big fire arriving at the burning building.A. byB. onC.

问题补充：

The fireman started to put out the big fire arriving at the burning building.

A. by

B. on

C. at

D. in

答案：

A. by

(答案→)B. on

C. at

D. in

解析：on 一…就…句意为“消防员一到达着火的楼房那就开始灭火”选B