望采纳 正关系代词as和which均可引导非限制性定语从句,均可指代主句所表达的整个内容或部分内容,均可在从句里充当主语、宾语或表语等。一般情况下,as和which可以互换,但在某些时候,两者却不可以互换。as与which可以互换的情况 1.在一个被动式的定语从句里作主语。例如:1)John got beaten in the game,as/which had been expected.约翰比赛失 利,这一点早在预料之中。2)Sophia was not unconscious,as/which could be judged from her eyes. 索菲娅并没有失去知觉,这可以从她的眼睛里看得出来。He failed this time, which I couldn't expected.他这次失败了,这是我未料想到了。定语从句为否定形式的,只能用which,不能用as。 as 引导的非限制性定语从句,可以在主句之前也可在主句之后,而which 引导的从句只能在主句之后