[单选] A Wang Xiaojun， a 12-year-old boy， lives in the countryside in Hubei Province． Today is his birthday． His parents have prepared a nice dinner for him， but the boy says， “I won"t have dinner because today is over after dinner and my parents are leaving for Shenzhen tomorrow． I don"t want to let them go． ” It is the first birthday that Wang Xiaojun has spent with his parents in three years． In the past three years， his parents have worked hard in Shenzhen to make money． They haven"t seen their son for three years． Tomorrow they will have to leave for Shenzhen again． Wang is not the only left-behind child（留守儿童）．In the countryside of China， there are more than 20 million children staying at home without their parents． Left-behind children face a lot of problems． Most of them stay with their grandparents． They get less care from their parents． They often feel lonely． Some of them don"t study well because their parents can"t help them with their lessons． The Chinese government cares about the left-behind children very much and is trying to solve their problems now．1． Why do the parents prepare a nice dinner for their son？