Mumbo the monkey has found a small box while walking down the street. “What's this?” Mumbo was curious （好奇） .Mumbo's friends started to talking one after another （一个接一个的议论） . “This is something that people keep money in.” “No, it's not. This is something you put mice （老鼠） in.” “No, it's not. This is something you store meat （储存大米） in.” “I think it's a magic box （魔法盒） .” Eventually （终于） , Mumbo and his friends decided to ask the child. “Hey, kid! Do you know what this is used for?” “This? You monkeys don't even know what this is used for?” “This is a milk carton （牛奶盒） that holds milk. Ha! Ha! Ha! ”The child left laughing.

Questions: What is this box used for?