Suppose that f is a function with a prototype like this:
void f(________ head_ptr);
// Precondition: head_ptr is a head pointer for a linked list.
// Postcondition: The function f has done some computation with
// the linked list, but the list itself is unchanged.
What is the best data type for head_ptr in this function?
A. node
B. const node
C. node*
D. const node*