I’ll never forget the days when I spent with you in Hangzhou. A B C DBwhen—that/which

问题补充：

I’ll never forget the days when I spent with you in Hangzhou.

A B C DBwhen—that/which

答案：

(答案→)Bwhen—that/which

解析：这是一个定语从句,从句中没有宾语,先行词为时间(物).