在不定代词anything, nothing, the one, all, much, any, few, little等作先行词指物时,只用that不用which.
在定语从句中关系代词做从句的宾语时可省略.
如the school is quite different from the one that it used to be 中
that做 used to be 的宾语,从句原为it used to be that/the one ,that代指先行词the one .故可省略that.