Consider the function f defined below, the function f returns 1 if and only if int list::f() { return f(head); int list:: f(node p) { return (p NULL) || (p->next == NULL) IT (( p->data != p->next->data) && f(p->next)) ); } Select one: O a. All elements in the list have different data values. O b. The elements in the list are sorted in non-increasing order of data value c. All elements in the list have the same data value Od. The elements in the list are sorted in non-decreasing order of data value