I think I was at school,      I was staying with a friend during the vacation when Iheard the news.[      ]

A. even so      

B. and then      

C. or else      

D. so that

根据《突发公共卫生事件应急条例》的规定，下列哪项是突发事件应急工作应当遵循的原则

A．预防为主，常备不懈

B．积极预防，认真报告

C．及时调查，认真处理

D．监测分析，综合评价

E．完善并建立监测与预警手段