5.9

#include<stdio.h>int main(){int score;printf("Input score:");scanf("%d",&score);if(score<=100&&score>=90){printf("A\n");}if(score<90&&score>=80){printf("B\n");}if(score<80&&score>=70){printf("C\n");}if(score<70&&score>=60){printf("D\n");}else if(score<60){printf("不合格\n");}return 0;}

运行结果