The old scientist made another great discovery ,______ of great importance to science.A which i think B which i think is C which i think it is D i think which

The old scientist made another great discovery ,______ of great importance to science.
A which i think B which i think is
C which i think it is D i think which

B which i think is
非限制性定语从句which is ……,这里的i think是插入语.
整句翻译：这位老科学家又有了一个对科学有重大影响的伟大发现.

B
非限制性定语从句,用which, I think是插入语

B which I think is