在引导定语从句时,什么时候用that什么时候用in which?that和which怎么区分?介词放在关系代词的前面时,

that 和which在定语从句中作引导词,既可指人也可指物.一般可以通用.Can you remember the story that/which I told you last week? 它们的区别主要体现在：
1.在有‘选择性’时,用which. There were so many books on the shelves. I really couldn't find the book which Mr Wang wanted to give me.书架上有那么多书.我确实找不出王先生要给我的那本.
2.主句中有who,the only one 等词时,用that,不用which. Who was the man that went with you?跟你一起去的人是谁? This is the only thing that I like.这是我唯一喜欢的东西.
3.如果引导词前有in,at等介词时,用which,不用that. This is the house in which my parents used to live.这是我父母过去常住的房子.

that 什么时候都可以用，which 只能修饰物体。
in which 其实就是whose ，是（.....的）的意思，在从句中做定语，修饰名词，比如说 father 。。。whose car 。。。此时,whose 指的就是父亲的。。。车，而that 没有这个意思。
（汗，想了好久，望采纳哈。）...

that只能用于限制性定语从句中，which既可用于限制性定语从句也可用于非限制性定语从句