——How did you pass the challenging test?
——It was a long time I found a series of suitable methods.
A. when
B. until
C. since
D. before
网友回答
A. when
B. until
C. since
(答案→)D. before
解析：考查时间状语从句。It is a long time before...花了好久才......。句意：--你是怎样通过那么难的考试的？--我花了好久才发现了一系列的适合我的方法。故选D。