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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.

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?
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.

New input: Article: Larry was on another of his underwater adventures but this time, it was different. He decided to take his daughter along with him. She was only ten years old. This would be her first trip with her father on what he had always been famous for. Larry first began diving when he was his daughter's age. Similarly, his father had taken him along on one of his adventures. Since then, he had never looked back. Larry started out by renting diving suits from the small diving shop just along the shore. He had hated them. They were either too big or too small. Then, there was the instructor. He gave him a short lesson before allowing him into the water with his father. He had made an exception. Larry would never have been able to go down without at least five hours of theory and another similar number of hours on practical lessons with a guide. Children his age were not even allowed to dive. After the first adventure, Larry's later diving adventures only got better and better. There was never a dull moment. In his black and blue suit and with an oxygen tank fastened on his back, Larry dived from boats into the middle of the ocean. Dangerous areas did not prevent him from continuing his search. Sometimes, his was limited to a cage underwater but that did not bother him. At least, he was still able to take photographs of the underwater creatures. Larry's first adventure without his father was in the Cayman Islands. There were numerous diving spots in the area and Larry was determined to visit all of them .Fortunately for him, a man offered to take him around the different spots for free. _ The diving spots afforded such a wide array of fish and sea creatures that Larry saw more than thirty varieties of creatures. Larry looked at his daughter. She looked as excited as he had been when he was her age. He hoped she would be able to continue the family tradition. Already, she looked like she was much braver than had been then. This was the key to a successful underwater adventure. 
 Answer: To protect himself from danger.
Solution:
Why did Larry have to stay in a cage underwater sometimes?