其实没有必要去深究，只要记住：
非限制性定语从句：as we all know,smoking is harmful to our health,which is known to all.........(关键在于health和is之间的逗号，有逗号的话就叫做非限制性定语从句，而且连接词用which，who等，但绝不能用that)
限制性定语从句：as we all know,smoking is harmful to our health as is known to all.........(这个health和is之间没有逗号，这样叫做限制性定语从句，连接词只能用as).
内容全部来源于网络收集，如有侵权，请联系网站删除：QQ：24596024