What will be the output of the following C code?

#include<stdio.h>
#define hello 10
main()
{
    #ifdef hello
    #undef hello
    #define hello 100
    #else
    #define hello 200
    #endif
    printf("%d",hello);
}

A. Compile C code B. Optimize code C. Preprocess code before compilation D. Execute code

A. #define B. #include C. #ifdef D. #pragma

A. To include a header file B. To define a macro C. To declare a constant D. To declare a variable

A. #ifdef B. #ifndef C. #if D. #else