He made another wonderful discovery of great importance to science.A. which I think it i

问题补充：

He made another wonderful discovery, of great importance to science.

A. which I think it is

B. which I think is

C. which I think

D. I think which is

答案：

A. which I think it is

(答案→)B. which I think is

C. which I think

D. I think which is

解析：考查插入语：句意：他做出了一个重大发现，我认为这对科学是非常重要的，which引导的是非限制性定语从句，I think是插入语，在which后面，去掉I think可知which是定语从句的主语，it是多余的，选B。