Kalakota和Whinston的柱状框架，将公共政策和技术标准看做是支撑（）基础设施的两根栋梁。①网络，②多媒体内容，③信息传递，④公共业务服务

A.①②③

B.②③④

C.①②④

D.①②③④

I went along thinking of nothing__________，only looking at things around me.[ ]

A．in particular      

B．in harmony

C．in doubt  

D．in brief