What will be the output of the following C code?

#include <stdio.h>
#define a 2
main()
{
    int r;
    #define a 5
    r=a*2;
    printf("%d",r);
}

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