He made another wonderful discovery, _______ of great importance to science.
A.which I think
B.which I think it
C.which I think is
D.I think which is
答案:C
题目分析:考查定语从句:句意:他又有了一个重大的发现,这我认为对科学是非常重要的。I think 是插入语,可以忽略,剩余的就是一个很明显的which指代前边整个句子(事实)引导的一个非限定性定语从句。Which在定语从句中做主语,it是多余的,定语从句中系表结构,is不能缺,还有插入语应该在which后面,选C。