1、关系代词可以用which，关系副词可以用who，when，where，why等
如：
Mr.zhang，who came to see me yesterday，is an old friend ofmine.
张先生昨天来看我，他是我的一位朋友.
His father is an engineer ，which makes him very proud.
2、that 一般不用逗号紧接先行词引导定语从句
如：He didn’t pass the exam，which disappointed me.
