He gave us another piece of advice of great help to the research work. A. which I think

问题补充：

He gave us another piece of advice, of great help to the research work.

A. which I think is

B. which I think it is

C. I think which is

D. I think it is

答案：

(答案→)A. which I think is

B. which I think it is

C. I think which is

D. I think it is

解析：考查从句，首先分析句子，从句of great help to the research work.缺少主语和谓语，又是个非限制性定语从句，所以选A