What is the output of the following code?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = 0;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

A. -1

B. 0

C. 1

D. runtime error

Answer: Option B