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Stamp collecting is an interesting hobby. You can learn many things, such as the geography of a country from stamps. Postal stamps are a source of interesting facts and important dates about every country in the world. It makes stamp collecting become very popular. As you look at the pages of a stamp album, you can learn interesting details of foreign customs, arts, literature, history and culture. Their colours can make you feel relaxed and happy. Collecting stamps can become a business. If you are lucky in finding a special stamp, it will bring you some money besides knowledge and pleasure.
Question: The main idea of the passage is____