初中英语课标要考定语从句，但是只考关系代词引导的定语从句，关系副词不考。

先行词是人的，由关系代词who和that引导，先行词是物的，由关系代词which或that引导，作宾语的可以省略，作主语的不能省略。He is a boy who is called Tom.这个句子中关系代词who做主语不能省略。This is the watch that his father bought for him.这个句子中关系代词that 做宾语可以省略。