管理菜单： 1] 建立成绩单 2] 查询某一成绩 3] 求全班同学的平均分 4] 将成绩从小到大进行排序 5] 输出所有学生的成绩 6] 求全班成绩的最高分 7] 退出菜单-Management menu: 1] the establishment of transcr ipts 2] query results in a 3] for the whole class' s average score 4] the results are sorted f