It is a long time they separated, but it won’t be long they meet again.
A. since, before
B. after, when
C. since, when
D. after, before
网友回答
(答案→)A. since, before
B. after, when
C. since, when
D. after, before
解析：句意：自从他们分开已经很长时间了，但是没过多久他们又相见了。Since自从，前面的主句也可用现在完成时；it won’t be long before…没过多久就…….这是固定句型。