1、定语从句中关系代词只能用which引导的几种情况(1)当关系词前面有介词时，指物常用which.The prize for which he worked so hard was a new bike.He built a telescope through which he could study the skies.(2)非限制性定语从句指物时，多用which.Bamboo is hollow, which makes it light.He wrote an article, which tells us about the computer.(3)如果先行词本身是that
2、时，只用which.This is that which he bought yesterday. (4) which还有一种特殊用法，它可以引导从句修饰前面的整个主句，代替主句所表示的整体概念或部分概念。在这种从句中，which可以作主语，也可以作宾语或表语，多数情况下意思是与and this 相似，例如： He succeeded in the competition, which made his parents very happy.
