A、Because it takes too long to process all the applications. B、Because its resources are limited. C、Because it is a library for

This library is an English language teaching and learning library.[19]Unfortunately our resources are limited and so not everyone can join. Teachers of English, university students and professionals who are in the medical, engineering, and management fields can all join the library. Those from other professions are welcome to apply. But your application will not necessarily be approved. You must fill in a library application form and put it in the box on the librarian’s desk. Because of the high number of applications we receive each week, you must wait one week. Please bring your student or work card to pick up your library cards. Library application forms which are not picked up within two months will be discarded and you will have to reapply.
    You may borrow one video at a time. The video must be returned in one week.[20]If you can’t return it on time, please call. Otherwise your video library card will be cancelled. You may borrow three items at one time.[21]That is three books or three cassettes. Items must be returned within one month. You can telephone the library to renew items for another month.
19. Why can’t the library issue library cards to everyone who applies?
20. What will the library do if a reader fails to renew the video when it is due?
21. For how long can a reader keep the book before he renews it?