I’m sorry you’ve been waiting for so long, but it’ll still be some time Brian gets back.
A. since
B. after
C. when
D. before
网友回答
A. since
B. after
C. when
(答案→)D. before
解析：A. since 自从B. after在…之后 C. when当...时候 D. before在…之前；句意：我很抱歉你等了这么长时间，但是在布莱恩先生回来之前还要一段时间。本题中it作为形式主语，before所引导的时间状语从句作为真正的主语，故选D