题目

It is good to get in touch with your inner child from time to time，and obviously some people are willing to pay big money for the chance to do so in a proper environment．A Brooklyn-based adult preschool is charging customers between $333 and $999 for the chance to act like a kid again． At Preschool Mastermind in New York adults get to participate in show—and—tell，arts—and—crafts such as finger paint，games like musical chairs and even take naps．The month-long course also has class picture day where the adults are expected to have a field trip and a parent day． 30-yea足球比赛中的应用． 裁判员用掷硬币的方法，确定哪个队先开球． 想一想，这是用了什么原理？