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