初学者在运用switch时遇到问题，求帮助

Question

不管输入什么分数都显示结果为E？
#include <stdio.h>

int main()
{
char score;
scanf("%c",&score);
printf("输入成绩：\n");
int a=score/10&&a<=10&&a>=0;
switch(a)
{
case 10:printf("A\n");break;
case 9:
case 8:printf("B\n");break;
case 7:printf("C\n");break;
case 6:printf("D\n");break;
case 5:
case 4:
case 3:
case 2:
case 1:
case 0:printf("E\n");break;
default:printf("输入错误!\n");
}
return 0;
}

Answer 1

int score;
printf("输入成绩：\n");
scanf("%d",&score);
int a=score/10;