英语定语从句中什么情况下只用that，不用which？又在什么情况下只用which，不用that呢？

（1）当关系代词紧跟介词，作介词宾语时，只能用which或whom，不能用that。但当介词位于从句句末时，仍可用that或省略。如：
This is the house about which we wrote to you.
Do you know the man to whom your brother writes?
I have read the book (which /that) you told me about.
（2）当先行词是all, everything, something, nothing等不定代词，或被first, last, only, few, much, some, no, any以及形容词的最高级修饰时，只能用that，不能用which。如：
All (that) they needed were qualified workers.
This is the most difficult book (that) I have ever read.
（3）在非限制性定语从句中，只能用which, who, as，不能用that。非限制性定语从句既可修饰先行词也可修饰整个主句，往往起补充说明的作用，并有逗号与主句隔开。如：
He was ill for a month, which set him back a lot in his work.
I want to buy a house, which has a garden.

有用请采纳，谢谢！

一.用that不用which
1）先行词是最高级或他前面有形容词最高级时
This is the best --that-- has been used against air pollution in cities.
English is the most difficult subject --that-- you will learn during these days.
2)先行词是序数词或它前面有一个序数词时
He is the last person --that-- i want to see.
3)主句中有疑问句
Which is the pen --that-- you lost?
4)先行词既有人又有物时
The bike and its rider --that-- had run over an old man were taken to the police station.
5)先行词是 all, much, little ,something,everything,anything,nothing,the one时
6）先行词前有 only,any,few,little,no ,all,one of,the same, the very等词装饰时
7）有2个定语从句，其中一个关系代词已用which，另一个应用that。
Tom built up a factory which produced things that had never been seen before.
二.用which不用that：关系代词前有介词
This is the school in --which-- you will study.
.原句本来就有that
Let me show you the book --that-- i borrowed from the library --which-- was newly open.

本人去寻笔记也