In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

Let me give you an example: Article: There are a lot of public libraries in Britain. These libraries have more than one hundred and fifteen million books, not including those libraries of public schools. Public libraries not only lend books, music records but also help children, patients in hospitals and others to get special play readings, film shows and so on. The first public libraries were founded in about the year 1850. Today's public libraries usually have a reading-room, a lending room and a reference room. The greatest and most famous library in Britain is that of the British Library in London. It was founded in 1973 and has over 10, 000, 000 books. It has nearly every magazine, newspaper and book published in Britain and other parts across the world.
Answer: 10,000,000 or less.
The answer to this example can be: How many books are there in the British Library?
Here is why: In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.

OK. solve this:
Article: The cost of college textbooks has risen sharply from 2002 to 2014. As a result, students have to look for other less expensive options , such as renting books. Now, they find another way, that is, using textbooks on the Internet, uploaded by other students. It is hard to know how popular this practice will be, but many college students around the country are uploading their expensive college textbooks onto the Internet, so that other students can download them for free and avoid the big fees. A year ago, a student wrote a blog called Children of the Stars about a professor who insisted that students buy the newest edition of a specific sociology book for more than $200 and didn't allow them to purchase an older paperback edition of the same book for $5. The student wrote, "The newest edition of the book is so expensive. Fortunately, we found the electronic one online, which is very cheap. This is why we downloaded. " The blog is followed by a list of websites where people can download books. Curious about how varied the selection of books was and how easy it was to download them, Vocativ.com decided to do an experiment. The workers of it picked five typical and important courses of freshmen and tried downloading all these textbooks on the websites offered by the student who wrote Children of the Stars. They typed the titles of these textbooks into a computer, and found them immediately. Within minutes, they had four textbooks on their hard drive. It is illegal to upload or download copyrighted materials without permission, but students still do it due to its advantages. Besides, schools haven't taken action to stop it.
Answer: Because it is lower in cost.
Answer:
According to the passage, why do many students choose to download textbooks?