C programming

10) Which of the following defines a recursive function for calculating the sum of number from 0 to n? A) I . L int sum (int n) { if (n==0) return 0; else return sum (n+ (n-1)); } B) int sum(int n) { if (n==0) return 0; else return n+sum (n-1); } C) int sum (int n) { if (n==0) return 0; else return n+ (n-1); }