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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: People who eat chocolate regularly tend to be thinner, new research suggests. The findings come from a study of nearly 1,000 US people that looked at diet, calorie intake and body mass index(BMI)----a measure of obesity. It found those who ate chocolate a few times a week were, on average, slimmer than those who ate it occasionally. Even though chocolate is loaded with calories, it contains ingredients that may favour weight loss rather than fat synthesis , scientists believe. Despite boosting calorie intake, regular chocolate consumption was related to lower BMI in the study. The link remained even when other factors, like how much exercise individuals did, were taken into account. And it appears it is how often you eat chocolate that is important, rather than how much of it you eat. The study found no link with quantity consumed. Lead author Dr. Beatrice Golomb, from the University of California at San Diego, said, "Our findings appear to add to a body of information suggesting that the composition of calories, not just the number of them, matters for determining their ultimate impact on weight." This is not the first time scientists have suggested that chocolate may be healthy for us. Other studies have claimed chocolate may be good for the heart. Consumption of certain types of chocolate has been linked to some favourable changes in blood pressure and insulin sensitivity. And chocolate does contain antioxidants which can help to absorb free radicals----unstable chemicals that can damage our cells. Mice fed for 15 days with epicatechin (present in chocolate) had improved exercise performance and observable changes to their muscle composition. They say clinical trials are now needed in humans to see if this is the case. But before you reach for a chocolate bar, there are still lots of unanswered questions. And in the absence of conclusive evidence, experts advise caution. While there's no harm in allowing yourself a treat like chocolate now and then, eating too much might be harmful because it often contains a lot of sugar and fat too.
Answer: Chocolate may help keep people slim.
Solution:
What is the passage mainly about?