单项选择题
【案例分析题】
During the summer session there will be a revised schedule of services for the university community.Specific changes for intercampus bus services，summer hours for the cafeteria，the infirmary（校医院）and recreational and athletic facilities will be posted on the bulletin board outside of the cafeteria.Weekly movie and concert schedules which are in the process of being arranged will be posted each Wednesday outside of the cafeteria.
Intercampus buses will leave the main hall every hour on the half hour and make all of the regular stops on their route around campus.The cafeteria will serve breakfast，lunch，and early dinner from 7a.m.to 7p.m.during the week and from noon to 7p.m.on weekends.The library will maintain regular hours during the week，but shorter hours on Saturdays and Sundays.The weekend hours are from noon to 7p.m.
All students who want to use the library borrowing services and recreational athletic，and entertainment facilities must have a valid summer identification card.This announcement will also appear in the next issue of the student newspaper.
Which of the following is the main purpose of this announcement?（）
