It was quite a long time____ I r

It was quite a long time____ I realized what had happened to the old man.
A、 after
B、when
C、since
D、before
【正确答案】：D
【题目解析】：考查时间状语从句。固定句型为“It wasbefore+一段时间从句”,表示过了很长时间才/就…”。而“Itis一段时sin间十从句”结构,其句意是“自从…以来已经很久了”,主句中的be动词多为现在时。所以,根据句意,选D【参考译文】过了很长时间我才意识到老人发生了什么事。