用于c ++中加法乘法的数学程序

Question

void additionmenu()
{
    char choice;
    printf("Please select the level");
    printf("A level 1");
    printf("B level 2");
    printf("C level 3");
    scanf("%c", &choice);
    if (choice == "A" || "a")
    {
        printf("You have selected level 1\n");
        additionmenu();
    }
    else if (choice == "B" || "b")
    {
        printf("You have selected level 2\n");
        subtractionmenu();
    }
    else if (choice == "C" || "c")
    {
        printf("You have selected level 3\n");
        multiplicationmenu();
    }
    else
    {
        printf("Invalid choice\n");

    }

错误发生在第58,63,68,84,96行

'==': 'int' differs in levels of indirection from 'char [2]'
 'time' undefined; assuming extern returning int    
illegal else without matching if

那些是错误......

有人可以帮助我解决问题 我必须开发一个数学测验程序 n有人可以告诉我如何为level1,2,3

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