7.　　编写一个程序，从键盘输入一批学生的成绩信息，每个学生的成绩信息包括：学号、姓名以及3门课的成绩。然后按照平均成绩由高到低顺序输出学生的学号、姓名以及平均成绩。-7. Write a program from the keyboard a number of student achievement information, information on each student' s accomplishments include: Student ID, name, and three class results. And then follow the order of the output from high to low grade point average of students of school number, name and grade point average.