Most London colleges have a library, with a full-time librarian who will be able to give students information on the facilities available for consulting or borrowing books. 　1　the Public Libraries give a valuable service to students 　2　colleges, evening classes or working 　3　. Public Libraries are maintained by the City Corporation and the various London Borough Councils. They will be helpful to students who wish to 　4　their studies by using the comprehensive library 　5　available in the metropolitan area. These libraries have over five million books in 　6　, the majority of which are for loan, and there is a system of inter- availability of 　7　tickets which extends 　8　the metropolitan area. Reference departments are provided for the use of those who wish to 　9　books and periodicals on library 　10　, or heavy publications such as encyclopedias which cannot be taken out 　11　.
　　Public library stocks are of a general nature, 　12　all subjects, many of them to higher degree standard or 　13　. In addition, each public library in the metropolitan area 　14　 in a group of inter-related subjects and, through the cooperation between various libraries, their  combined 　15　are made generally available 　16　, through the inter-lending system of the British Library（Lending division），it is usually possible for books not available in London public libraries 　17　from specialist libraries. Music 　18　, for example，include miniature scores and 　19　records. Full details of these various services can be obtained from the Central Library in each area. Addresses and telephone numbers are fisted in the London telephone  　20　.
______

A.function 

B.service

C.books

D.sources