He made another wonderful discovery, ________ of great importance to science.
A. which I think is B. which I think it is
C. which I think D. I think which is
He made another wonderful discovery, ________ of great importance to science.
A. which I think is B. which I think it is
C. which I think D. I think which is
【解析】选A。考查非限制性定语从句及插入语。此处I think为插入语,which是引导定语从句的关系代词。