—Though it is 30 years we last met, I still remember the sce

—Though it is 30 years we last met, I still remember the scene we go
—Though it is 30 years we last met, I still remember the scene we got separated on a rainy day.
A．before; where B．before; which C．since; when D．since; where
【答案】D
请分析说明一下选这个答案的原因和理由,谢谢!