题目

The professor has written another book ____ of great importance to computer science. A. which I think it is B. and I think isC. which I think is   D. when I think is 答案：C 解析: I think是插入语。A答案中的it是多余的。如图是某农场温室大棚中增加二氧化碳浓度的一种仪器，大棚中安装这种仪器的目的是什么？原理又是什么？