只用that不用which旳情况
1)当先行词是不定代词all,everything , something , anything , little , much等时e.g.Is there anything that I can help you? e.g.That is all I want to say.2)当先行词被序数词所修饰时e.g.This is the second book that was written  by the writter.              
3)当先行词被形容词旳最高级修饰时，  e.g.  This is the best film that I have ever seen.  4)当先行词前有限定词noly , very,little,just等修饰时, e.g. This is the very dictionary that I want to buy. e.g. There is little time that we can use.
5)在there be句型中，只用that，不用which  e.g. There is a ...