—— 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：考查固定句型：句意：--你是怎么通过这个有挑战性的考试的？--我们还要有一段时间才能找到一系列适合的方法。这句话用了句型：It was/will be+一段时间+before..，要多久才…，选D。