问题补充:
The professor has written another book of great importance to computer science.
A. which I think it is
B. and I think is
C. which I think is
D. when I think is
答案:
A. which I think it is
B. and I think is
(答案→)C. which I think is
D. when I think is
解析:I think是插入语。A答案中的it是多余的。