I’ll never forget the days I spent in Beijing last year.A. whenB. on whichC. in whichD. t

I’ll never forget the days I spent in Beijing last year.
A. when
B. on which
C. in which
D. that

A. whenB. on whichC. in which(答案→)D. that解析：可联系答.案.网客服索取。

我明天再问问老师，叫他解释下这个问题