--- ________ did your uncle leave his home town?.

--- Let me see. He _______ for nearly twenty years.

A．When; has left

B．When; has been away

C．How long; has left

D．How long; has been away

发生公共危机事件后，政府各部门应该扮演公共危机管理机构的什么角色（）？

A、综合协调机构

B、职能组织机构

C、最高决策机构

D、决策咨询机构