1.在非限制性定语从句中只可用which,不可用that.
2.which 只能指代人;that可以指代人,也可指代物
3.如果出现what,要看它在从句中作什么成分,并且还要看主句缺少什么成分.eg:I don't know what he has done.这个句子what he has done就是个宾语从句,应为主句I don't know 缺少宾语.
1.在非限制性定语从句中只可用which,不可用that.
2.which 只能指代人;that可以指代人,也可指代物
3.如果出现what,要看它在从句中作什么成分,并且还要看主句缺少什么成分.eg:I don't know what he has done.这个句子what he has done就是个宾语从句,应为主句I don't know 缺少宾语.