There must be a better way to teach our students __________value of __________life than just inviting an old professor to give a boring lecture.    

A．the；a

B．／；the

C．a；the

D．the；／

有以下程序：
#include ＜stdio.h＞
main()
int c;
while((c=getchar() )! ='\n')
switch(c-'2')
case 0: case 1: putchar(c+4);
case 2:putehar(c+4);break;
case 3:putchar(c+3);
default:putchar(c+2);break;



运行程序，从第一列开始输入以下数据：
2473＜回车＞
则程序的输出结果是( )。

A) 668977
B) 668966
C) 66778777
D) 6688766