scanf("%C", &x)
reads only one character from the input stream, but when the user enters his choice, he probably presses 'A', then presses [Enter], so the input stream is actually "A\n", where '\n' is the new-line character. You should probably do something like
char x;
scanf("%c%*s", &x);
The "%C" format specifier for scanf expects a type
wchar
, so you should either change the definition of x to wchar, or change the format to "%c" (note uppercase vs lowercase).
What happens if the user enters 'X' or 'a'? Maybe you should do something about that?