(错)The tree, that is four hundred years old, Is very famous here.
We depend on the land from which we get our food.
We depend on the land that/which we get our food from.
(a) 在there be 句型中，只用that，不用which。
(b) 在不定代词，如：anything, nothing, the one, all等作先行词时，只用that，不用which。
(c) 先行词有the only, the very,the same,the last,just修饰时，只用that。
(h)先行词是the way或the reason时，that可作关系副词，也可省略
(i) 主句的主语是疑问词who /which时
1.先行词是all,any,everything,anything,nothing ,something,much,little,few,none ,the one 等时① There is much that should be used.
② You can take any seat that is free.
2.先行词被all,any ,no,only,little,much,very,every,some,few,none 等修饰时① I have read all the books (that) you gave me.
② Every dictionary that our library bought is good.
3.当先行词前有形容词的最高级修饰时① This is the most interesting book that I have ever read.
4.先行词前有序数词修饰时,包括 the last.① The first lesson that I learned will never be forgotten.
② The Great Wall is the last place that Mr.Smith is going to visit before he leaves Beijing.
5.在以 which,who作主语的.特殊疑问句中的定语从句中① Who is the man that is reading a book there?
② Which is the magazine that you borrowed from the reading room?
6.当先行词既有表示人又有表示物的词时① We talked of the things and persons that we remembered.
7.当先行词在定语从句中做表语时,无论先行词是人还是物① China is no longer the country that she was.
8.主句以there be 开头时① There is little that I can do to make up for the lost time.