进行初步的国民经济评价和初步的财务评价，是（）阶段的主要内容之一。
A.项目建议书
B.预可行性研究
C.可行性研究
D.初步设计
参考答案：B
无缝线路焊接接头矢度值有何规定？
I have been studying for two hours. Can I stop _______and play computer games for a while? [ ]
A. to have a rest
B. having a rest
C. to having a rest
D. have a rest
