C语言写一个菜单，功能1为将输入数字成绩转换为等级ABC，功能二为统计不同等级的人数

#include <stdio.h>

int main() {
    int option;
    int grade;
    int countA = 0, countB = 0, countC = 0;

    do {
        printf("\n--------------------------\n");
        printf("1. 将输入数字成绩转换为等级ABC\n");
        printf("2. 统计不同等级的人数\n");
        printf("0. 退出\n");
        printf("请选择功能：");
        scanf("%d", &option);

        switch (option) {
            case 1:
                printf("请输入数字成绩：");
                scanf("%d", &grade);
                if (grade >= 90) {
                    printf("等级：A\n");
                }
                else if (grade >= 80) {
                    printf("等级：B\n");
                }
                else if (grade >= 70) {
                    printf("等级：C\n");
                }
                else {
                    printf("等级：D\n");
                }
                break;
            case 2:
                printf("A级人数：%d\n", countA);
                printf("B级人数：%d\n", countB);
                printf("C级人数：%d\n", countC);
                break;
            case 0:
                printf("谢谢使用！\n");
                break;
            default:
                printf("无效选项，请重新选择！\n");
                break;
        }

        if (option == 1) {
            if (grade >= 90) {
                countA++;
            }
            else if (grade >= 80) {
                countB++;
            }
            else if (grade >= 70) {
                countC++;
            }
        }
    } while (option != 0);

    return 0;
}