i'll never forget the days we spent together on the beach last summer.a.which b.on which c.when

问题描述:

i'll never forget the days we spent together on the beach last summer.a.which b.on which c.when

用a吧
which这里好像是做代词代替了先行词days(when好像一般是做状语,不做代词)
至于介词,是当which后有不及物动词时,且动词后不借介词(即介词前移),与动词搭配的那个介词才放在which前.这个句子中spend为及物动词(可以理解为spend the days),所以不前提.
个人拙见,