What will be the output of the following C code?

#include <stdio.h>
#include <stdarg.h>
int f(...);
int main()
{
    char c = 97;
    f(c);
    return 0;
}
int f(...)
{
    va_list li;
    char c = va_arg(li, char);
    printf("%c\n", c);
}

A. Compile time error

B. Undefined behaviour

C. 97

D. a

Answer: Option A