2012考研必备：考研英语语法精要(40)

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5.关系代词that与which用于引导定语从句的区别
    (1)如果关系代词在从句中做宾语，用that, which都可以，而且可以省略；
    (2)先行词是不定代词anything, nothing, little, all, everything时，关系代词用that；
    (3)先行词由形容词最高级或序数词修饰或由next，last, only, very修饰时，用that；
    (4)非限定性定语从句只能用which引导；
    (5)关系代词前面如果有介词，只能用which。
   
    6.but做关系代词，用于否定句，相当于who…not, that…not
    这个结构的特点是主句中常有否定词或含有否定意义的词。如：
    There are few teachers but know how to use a computer.
    There is no complicated problem but can be solved by a computer.