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

问题补充：

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

答案：

(答案→)A. which I think is

B. which I think it is

C. which I think

D. I think which is

解析：考查定语从句。句中I think为插入语，which指代先行词discovery，在从句中作主语。句意：他又有一个极好地发现，对科学有重要的作用。