Question

which,in which,on which,for which ,of which 有什么区别，在定语从句中怎么用？

如：That is the day ( ) I'll never forget.
A.which B.on which C.in which D.when

Answer 1

选A。
which在限制性定语从句中就是指先行词，如题中的which就指先行词the day,在从句中作动词forget的宾语。
"介词+which"不能只从意思上区别，介词的选择主要有3方面
1，考虑先行词与介词的固定搭配。
This is the farm on which he is working .
on the farm 是固定搭配。
2，考虑句意的需要。
This is a factory into which he wants to go .
go into the factory .
He is one of my friends with whom i am living .
live with sb .
3, 考虑 定语从句谓语动词的固定短语所需什么介词。（这种情况尤为多些）
This is a book in which i am interested .
be interested in sth .

Answer 2

in which可以翻译成在……里面
for which可以翻译成为了……目的
on which可以翻译成在……的上面，或具体时间的某一天
at which可以翻译成在……里面或在……上面

追问

那at which 和in which有什么区别，for which 和at which 呢？？