In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.

Let me give you an example: Article: Homework can put you in a bad mood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Question: Researchers did experiments on kids in order to find out _ .
Options: (A) how they really feel when they are learning (B) whether mood affects their learning ability (C) what methods are easy for kids to learn (D) the relationship between sadness and happiness
The answer to this example can be: B
Here is why: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment. So, B is the correct answer.

OK. solve this:
Article: 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.
Question: What is the main purpose of this text?
Options: (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:
B