只能用that,不用which 的情况：
(1) 先行词是all, few, little, nothing, everything, anything 等不定代词时。如：
All that he said is true.
(2) 如果先行词被形容词最高级以及first, last, any, few, much, no, some, only, very等词修饰，关系代词常用that,不用which。如：
This is the best book (that) I have read this year.
This is the only book that the old woman is interested in.
(3) 先行词是序数词或被序数词修饰的词。如：
It was the second house that I bought.
(4) 先行词既包括人又包括物时。如：
He talked about the people and the things that he remembered.
（5）当主句是以who，which开头的特殊疑问句或先行词是who时，只能使用“that”
Which is the book that he borrowed from the library yesterday?
只使用which，不能用that的情况：
(1) 在非限制性定语从句中。如：
I will take this one, which was exactly what we wanted.
(2) 定语从句由介词+关系代词引导，先行词是物时。如：
The thing about which he is talking is of great importance.
(3) which的特殊用法，它可以引导从句修饰前面的整个主句，which可以作主语，也可以作宾语或表语，多数情况下意思是与and this相似。如：
He succeeded in the competition, which made his parents very happy.
