使用that的情况： 1.当先行词是nothing, something, anything, all, each等不定代词时。 2.当先行词被all, any, some, no, not, every, each等修饰时。 . 3.当先行词被形容词最高级、序数词所修饰时。 . 4.主句是以which或who开头的特殊疑问句时 . 5.当先行词在从句和主句中都作表语时,无论先行词是人还是物. 6.如有两个定语从句,其中一个已用which引导,另一个宜用that . 7.在there be句型中,只用that. 8.当先行词被the very, the last, the next, the only 等词修饰时 9.当先行词又有人又有物时。. 只能使用which的情况。 1、非限制性定语从句中。 e.g. Mary has a book, which is very precious. 2、在介词之后。 e.g. This is a house in which lives an old :man. 3、当主句中的主语被that修饰时。 e.g. That dog which I found in the street belongs to Mary.