You need to understand the requirements that/which are important to customers.
This is the cup that/which was bought by my mother.
The book which/that I borrowed from Jane was interesting.
= The book I borrowed from Jane was interesting.
She has the design for which she is admired by her colleague.
C.若先行词有all, everything, little, much, none, nothing等时，用that
There is nothing (that) you can do.
This is all that I want to say.
There wasn't much that she couldn't do.
There is little water that can be used.
This is the most interesting movie (that) I have ever seen.
This is the best price that is available.
It was the first movie that I saw.
F．先行词有the very/the only/the same等修饰时，常用that
This is the very bag that I want to buy.
The only thing that I can do is to move on.
My hometown is no longer the town (that) it used to be ten years ago.
She talked about earth and men that Aristotle once talked about.
Which is the car that you bought last month?
Which is the bag that you mentioned?
J.强调句中，用that： It is….that….
It was orange juice that I ordered.
It was the exam that made him nervous.
It was that which caused the accident.
That which is mortal is not immortal.
The bike, which I bought last month, seats three people.
She played football, which is a sport different from basketball.
以上就是定语从句中关系词that which的区别，希望对你有所帮助。你可能还想进一步查阅：定语从句that which省略