用安卓系统编写的一个简单小学生四则运算出题软件。满足自动出题，自动计时，统计正确/错误/留空等数据。自动计时5分钟，时间到则自动统计结果。-Use android to develop a operator quiz app. It can automatically form a question and the result will be shown at the end. A timer is also used.