在非限制定语从句中用which，as有什么区别

解答: 

which 和as 都可以引导非限制性定语从句，它们的先行词都可以是前面的整个句子，但在用法上有区别。它们的区别是：

1. which引导的非限制性定语从句必须置于主句之后，而as引导的非限制性定语从句可以置于句首、句中和句尾。例如：

1)She has been admitted to Beijing University, which / as is true.她考上北京大学了，这件事是真的。

2) As is known to all, China is famous for the Great Wall. 众所周知，中国以长城而闻名。

3)Taiwan, as is known to all, belongs to China. 众所周知，台湾是中国的一部分。

4) China is a developing country, as is known to all. 众所周知，中国是一个发展中国家。

   2. as有“正如……，正像……”的意思，而which则没有。例如：

1）As you can see, we're still working. 如你所见，我们仍在工作。

2）There are two people who have been admitted to Shandong University , as we expected. 正如我们所预料的，有两个人考上山东大学。

   3. which可以用在名词之前，而as则不可以。例如：

1）He has been absent from work for two months, in which case the boss will have to consider dismissing him. 他已经旷工两个月了，既然这样，老板将不得不考虑解雇他。

2）Mary is in hospital, for which reason she cannot go to school. 玛丽住院了，由于这个原因，她不能去上学。