请给我介绍中国古代四大发明，并将每个发明的回答控制在50字以内，以英文输出。
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Papermaking: Invented in Han Dynasty, revolutionized writing and information dissemination.  
Compass: Originally used for feng shui, later for navigation, enhancing exploration.  
Gunpowder: Discovered by alchemists, used in warfare, changing military tactics.  
Printing: Movable type printing, facilitated mass production of books.
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