What does the following C statement declare?

int (*f)(int *);

Consider the following C program:

double foo(double); /* Line 1 */
int main () {
  double da, db;
  //input da
  db = foo(da);
}
double foo(double a){
  return a;
}

The above code compiled without any error or warning. If Line 1 is deleted, the above code will show:

Consider the following C program:

void foo (int n, int sum) {
  int k = 0, j = 0;
  if(n==0) return;
  k=n%10; j = n /10;
  sum = sum + k;
  foo(j, sum);
  printf("%d",k);
}
int main () {
  int a = 2048, sum = 0;
  foo(a, sum);
  printf("%d\n", sum);
}

What does the above program print?

Which one of the following are essential features of an object-oriented programming language?
i) Abstraction and encapsulation
ii) Strictly-typedness
iii) Type-safe property coupled with sub-type rule
iv) Polymorphism in the presence of inheritance