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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: prefix = st1 /Britainis facing a sharp rise in its rat population as growing numbers of people leave fast food scraps in the street , an environment group warned . Keep Britain Tidy said the rodents  were stopping their traditional hunts underground and were roaming the streets ,tempted by discarded burgers ,pizzas and crisps. "The rat population is on the rise and soon it'll be as common to see a rodent on our street as it is to see a dog or a cat," said group Director ,Sue Nelson. The practice of dumping fast food litter and scraps on the street rather than in the trash-with young men the worst offenders-was behind the rise. According to the National Rodent Survey in 2005, Britain's rat population has grown by nearly one quarter since 2000 and is now estimated at 60 million , two million more than the human population. On average a rat can give birth every 24--28 days and just a single pair of rats can produce a colony of 2,000 a year. Around 200 people a year get Weil's Disease----an infection which can lead to liver or kidney  failure and eventually death and which is arrived in rat's waste. To highlight the issue , Keep Britain Tidy launched a cinema ad entitled "How close do you want them to get?" The advertisement gave a shocking image of a young woman sleeping in a bed of rots, echoing the nightmare scene from James Herbert's classic horror tale The Rats, in which mutant rodents begin to prey on humans. 
 Answer: Under the ground.
Solution:
Where did the rodents use to search for food?