选A.
主干是The fire is still seen burning now.大火现在被看到仍然在烧.be seen doing表某事被看到正在被做;
其余部分是定语,修饰the fire,用完整的定语从句表达应该是:the fire which broke last night(break为不及物动词,无被动语态),which broke 表主动,可用现在分词breaking作定语修饰名词
明白了吗?