College libraries are designed primarily for research and study. To explain its use, let us choose a research topic and follow the step-by-step procedure of looking up the material for the paper. Suppose your assignment is to write a paper on a novel called The Sun Also Rises by American writer Hemingway.The first step is to go to the main catalog.Many small drawers on the large wooden cabinets are lined up in alphabetical  order.Each of the drawers contains hundreds of alphabetical ordered cards.These cards are printed references to all material available in the library.Title cards are cataloged by the first word of the book title, leaving out the articles like "a", "an" and "the".And then you get the cards for the books you need.On the upper left corner of each card is the call number.This is the numerical code that shows where the book is located in the library.The library has open and closed stacks.If your book is on the open stacks, you can go to the open-stack room, and according to the call number find it out by yourself.There are only about 30,000 books on open stacks, while most of the 800,000 books in our library are kept in closed stacks, which are accessible only to teachers and graduate students. For undergraduates like you, borrowing books from the closed stacks have to be done with the help of our librarian.In that case, you must fill out a call slip  for the book, showing the call number, author and title.You can get call slips on tables near the catalog cabinets.You show your call slip together with your library card to a librarian at the information desk.He or she will help you find the book out in the closed stacks. What is the main purpose of this text?
To present readers a brief introduction to a college library. To guide readers how to find books needed in a college library. To tell readers how to fill out a call slip in a college library. To show readers where to find books in a college library.
Question: College libraries are designed primarily for research and study. To explain its use, let us choose a research topic and follow the step-by-step procedure of looking up the material for the paper. Suppose your assignment is to write a paper on a novel called The Sun Also Rises by American writer Hemingway.The first step is to go to the main catalog.Many small drawers on the large wooden cabinets are lined up in alphabetical  order.Each of the drawers contains hundreds of alphabetical ordered cards.These cards are printed references to all material available in the library.Title cards are cataloged by the first word of the book title, leaving out the articles like "a", "an" and "the".And then you get the cards for the books you need.On the upper left corner of each card is the call number.This is the numerical code that shows where the book is located in the library.The library has open and closed stacks.If your book is on the open stacks, you can go to the open-stack room, and according to the call number find it out by yourself.There are only about 30,000 books on open stacks, while most of the 800,000 books in our library are kept in closed stacks, which are accessible only to teachers and graduate students. For undergraduates like you, borrowing books from the closed stacks have to be done with the help of our librarian.In that case, you must fill out a call slip  for the book, showing the call number, author and title.You can get call slips on tables near the catalog cabinets.You show your call slip together with your library card to a librarian at the information desk.He or she will help you find the book out in the closed stacks. What is the main purpose of this text?
A. To present readers a brief introduction to a college library.
B. To guide readers how to find books needed in a college library.
C. To tell readers how to fill out a call slip in a college library.
D. To show readers where to find books in a college library.
Answer: