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Li Chengze is a 12-year-old boy. He lives his parents in a big city. Now everyone calls him a little hero. One night it was very dry（干的） cold. He went home at about 22: 00.  he got to an entrance（入口） of his building, he smelled （闻） a smell of pungent （刺鼻的） gas. He quickly ran to the guard room（门卫室）, then he knocked（敲门）on the door from house to house with the worker. And he told people to open the windows and not to smoke. At   he found the place where    the smell came from. Thanks to the boy, nobody in the building got hurt in the accident.  clever Li Chengze is!