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.

Q: Article: Air traffic controllers in the US have been advised to take 26-minute naps , after a series of accidents involving workers falling asleep. Now the National Transportation Safety Board (NTSB) is calling for "controlled naps" during nightshifts . NTSB member Mark Rosekind said that a 26-minute nap would improve performance by 34%. He believes that beyond the aviation industry, other professions, such as motoring and machinery, also carry obvious risks. But other experts doubt whether 26 minutes is the appropriate napping time. It's a bit too long and risks you falling into a deep sleep, says Jim Horne, director of the Sleep Research Council. He said, "A nap of about 15 minutes is best; once you get beyond 20 minutes, you risk a deep sleep and you can be much more tired when you wake up. Therefore, we suggest that a nap be combined with a cup of coffee so that you can enjoy an effective sleep before the caffeine takes effect in 20 minutes. However, this method only works on those who have had a poor night's sleep. If you haven't had a sleep the night before, this method won't be enough to make you fresh." Health writer, Linda Wasmer Andrews, also believes that 26 minutes is too long. She says a nap between 10 and 20 minutes is enough, and the timing of the nap is also important. Putting your head down too early means your body may not be ready to sleep yet, but a nap that is too late in a day might make it harder to fall asleep. Early afternoon is often the best time, between l pm to 3pm, when people experience a post-lunch decrease in energy.
Answer: How long a nap should last.

A: What does the text mainly talk about?
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Q: Article: World Wrestling Entertainment is the largest professional wrestling organization in North America. It was called World Wrestling Federation until it changed its name because of a legal dispute. Its more than one hundred wrestlers fight each other in competitive matches that are written and practiced before they are performed. Professional wrestlers are athletes but act as entertainers. They are not seeking athletic records, but instead want to excite an audience. To do this, they use unusual names and wear special clothing during wrestling matches. These wrestlers include the Stone Cold Stunner and the Undertaker. Most professional wrestling matches are between two men or two women. They fight inside an area called a ring that is separated from the audience by ropes. Each match continues until one wrestler forces the other's shoulders to the floor and holds them there for a count of three. Most World Wrestling Entertainment matches continue for only about four to seven minutes. An organization official called a promoter decides before the match who will win. But who wins and who loses is not the important thing in professional wrestling. The important thing is that the audience enjoys the pretend fight. Some wrestlers rarely win, but continue to be popular. Not all wrestling matches are between two people. Some are called tag team matches and involve teams of two, three or four wrestlers. Another kind of match is called a battle royal. It involves thirty to sixty wrestlers competing against each other. A wrestler loses when he or she is thrown out of the ring. The winner is the last wrestler still standing.
Answer: Because maybe there was another name similar to it.

A: Why did World Wrestling Federation change its name?
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Q: Article: Some wonderfully creative uses of X-rays have been in the world of art.But the most impressive one is to uncover what has been covered up.Details unfolded by an X-ray of a painting can ' t be seen any other way.For example, in the past, paintings were often repaired if small pieces of paint fell off the canvas . These repairs cannot be seen just by looking at the painting.It takes an X-ray to discover where the repairs have been made. An X-ray of a painting is one of the best ways to tell if it was created by a famous painter or if it is a forgery .If there is a question as to whether an old master has painted a certain painting or not, X-rays are made and compared to those of paintings that are known to be original.If the brushstrokes , for example, are shown to be totally different than in other work done by a certain artist, then the painting is proved to be a fake copy. Since modern paints are usually made from different materials than paints of hundreds of years ago, the image they leave on an X-ray film looks different.This is another way X-rays can be used to spot a forgery.A modem artist will try to make a forgery look hundreds of years old by painting dirty varnish on it or by using artificial means to get the varnish to look cracked.To the naked eye the forgery may look old, but when a careful study of the X-ray image is made, the _ is obvious. It was common many years ago for an artist to finish a painting, decide it wasn't any good, and paint a completely different picture on top of it.Or artists would paint over others' work --it was their version of recycling.Taking an X-ray is the only way to find out if there is a picture underneath the picture you see with your eyes.Sometimes museums will be more interested in the painting beneath than the one on top, and will restore the older one by having the top layer painstakingly removed.
Answer: To help artists restore damaged artwork to its original appearance.

A:
What is the main purpose of the article?
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