Question

Edison made a lot of inventions, ________ of great importance．

1. A.
   which I think are
2. B.
   which I think they are
3. C.
   which I think they
4. D.
   I think which are

Answer 1

A
I think是插入语。which是关系代词，其先行词是inventions，引导非限制性定语从句。