The fire started on the second floor and it wasn't long the whole building was burned down.
A. while
B. when
C. after
D. before
网友回答
A. while
B. when
C. after
(答案→)D. before
解析：考查连词 句意为：大火在第二层楼开始蔓延，不久整栋大楼就被烧毁了。it isn’t/wasn’t long before 结构意为“不久…就…”；It +be+时间段+before结构意为“...之后才... ”