试着对以下的日程活动的安排进行排序(在空白处填上每个活动的字母即可,不用添加空格)。
A. A group discussion on how to improve the community services
B. Everything ending at 11 : 00 a.m.
C. A brief introduction about our community
D. Some visits to the community library,learning center and health service center
E. A presentation about community construction