Which of the following defines a recursive function for calculating the factorial of a number? a) int fact(int n) { if (n==1) return 1; else return fact(n*(n-1)); } b) int fact(int n) { if (n==1) return 1; else return n*(n-1); } c) int fact(int n) { if (n==1) return 1; else return n*fact(n-1); }