Teacher: 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.
Teacher: Now, understand the problem? If you are still confused, see the following 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.
Solution: How many books are there in the British Library?
Reason: In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.

Now, solve this instance: Article: Think about the longest elevator ride that you've ever taken. Whether you rose five or 100 floors, it probably took less than a few minutes. Now imagine riding in an elevator higher and higher as it climbs for nearly a day. When you reach the top floor, prepare for views that are really out of this world. You'll be in space! Space elevators might sound like a crazy idea, but they're something scientists have been working on for decades. At the moment, riding in a capsule is the only way ordinary people can get to and from space. But those rides are very expensive---about $ 25 million per person per flight. Now scientists are making efforts to reduce the expense of those rides. Researchers are still figuring out the details about how a space elevator might work. One idea is stretching a very long cable -- more than 37,000 kilometers -- up to space from the earth's equator . Objects in space above the equator orbit (......) the earth at the same speed that our planet turns. A weight on the end of the cable would stretch it tight. An elevator tied to the cable could use _ to climb up and down. The only problem is that besides being long, this cable must also be very strong. Storms, including hurricanes might break it. One way to solve this problem is to stretch the cable from the moon instead of from the earth. Airplanes designed to climb higher than a typical jet might take off from the earth and link up with the cable, which would be held in place by the pull of gravity from the earth. An elevator car waiting there would then take riders the rest of the way to the moon. Fueled by solar power, the elevator could transport people and materials without much expense or effort per ride.
Answer: To make trips to space cheaper.
Student:
Why have scientists been working on space elevators?