You have to find the sum of digits of a number given that the number is always greater than 0. Which of the following base cases can replace the base case for the below code?

#include<stdio.h>
int recursive_sum_of_digits(int n)
{
      if(n == 0)
        return 0;
      return n % 10 + recursive_sum_of_digits(n/10);
}
int main()
{
      int n = 1201;
      int ans = recursive_sum_of_digits(n);
      printf("%d",ans);
      return 0;
}

A. if(n == 0) return 1

B. if(n == 1) return 0

C. if(n == 1) return 1

D. no need to modify the base case

Answer: Option D