Question

我记得好像定语从句有一种情况！只能用that和which中的一种 而不能两者通用。是什么情况？？？

Answer 1

以下情况多用that.
(1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。例如：
All the people that are present burst into tears.
Is there anything that I can do for you?

(2) 如果先行词被the only, the very, the same, the last, the best等词修饰，关系代词常用that(指人时，可以用who),例如：
This is the very book that I want to find.
That is the best film that we have seen.
I was the only person in my office that/who was invited.

(3) 当先行词被all, every, no, some, any, little, much所修饰时；
You can take any seat that is free.

(4) 当先行词被序数词或形容词最高级所修饰时。
It is the first foreign book that I have ever seen.
This is the most beautiful flower that I have seen.

(5) 在there be句型中，常用that.
There is a man that lives in that village.

(6) 先行词有两个，一个指人，一个指物，关系代词应该用that。例如：
The boy and the dog that are in the picture are very lovely.

以下情况用which.
(1) 当关系词前面有介词时，指物常用which.
The prize for which he worked so hard was a new bike.
He built a telescope through which he could study the skies.

(2) 非限制性定语从句指物时，多用which.
Bamboo is hollow, which makes it light.
He wrote an article, which tells us about the computer.

(3) 如果先行词本身是that时，只用which.
This is that which he bought yesterday.

(4) which还有一种特殊用法，它可以引导从句修饰前面的整个主句，代替主句所表示的整体概念或部分概念。在这种从句中，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，例如：
He succeeded in the competition, which made his parents very happy.

Answer 2

非限定性定语从句只用WHICH 介词提前只用WHICH、、、、、 (1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。例如：2) 如果先行词被the only, the very, the same, the last, the best等词修饰，关系代词常用that(指人时，可以用who), 3) 当先行词被all, every, no, some, any, little, much所修饰时
4) 当先行词被序数词或形容词最高级所修饰时5) 在there be句型中，常用that.
(6) 先行词有两个，一个指人，一个指物，关系代词应该用that。

Answer 3

先行词既指人 又指物时用that