题目内容：
根据以下材料回答题 Inperiodofthesummerholidaystherewillbearevisedschedule(修改过的时刻表)ofser-vicesforthestudents．Changesfordining-roomandlibraryservicehoursandforbusscheduleswillbepostedonthewalloutsidethedining-hall．Weeklyfilmandconcertschedules,whicharebeingarranged(安排),willbepostedeachWednesdayoutsidethestudentclub．
Duringthesummerholidays,busesgoingtothetowncentrewillleavethemainhalleveryhouronthehalfhourduringtheday．Thedining-roomwillservethreemealsadayfrom7:00a．m．to7．"00p．m．duringtheweekandtwomealsfromnoonto7:00p．m．onweekends．Thelibrarywillcontinueitsusualhoursduringtheweek,buthasshorterhoursonSaturdaysandSundays．Theweekendhoursarefromnoonto5:00p．m．
Allstudentswhowanttousethelibrarylendingservicesmusthaveanewsummercard．Thisannouncementwillalsoappearinthenextweek'sstudentnewspaper．
Themainpurposeofthistextisto__________． A．tellstudentsofimportantschedulechanges
B．tellstudentsofnewbusandlibraryservices
C．showtheexcellentservicesforstudents
D．askstudentstorenewtheirlibrarycards
参考答案：
答案解析：