A young man goes to the city and buys himself(他自己) a pair of socks. When he comes back home, he goes to his room and tries them on. He finds they are in different colours. One is blue and the other is green. He goes into the kitchen. His mother and his sister are cooking dinner. He says to them, "The new socks are in different colours. I should make them in the same colour. Would you like to do this for me?" His mother and sister are very busy and they don't say anything. When his mother finishes(结束) cooking, she goes to her son's room and changes the green sock into blue. She comes back without(没有) saying a word to her son. After supper, his sister goes to her brother's room and changes one blue sock into green without saying anything to anyone.