The following function reverse() is supposed to reverse a singly linked list. There is one line missing at the end of the function. /* Link list node */ struct node { int data; struct node* next; };   /* head_ref is a double pointer which points to head (or start) pointer of linked list */ static void reverse(struct node** head_ref) { struct node* prev = NULL; struct node* current = *head_ref; struct node* next; while (current != NULL) { next = current->next; current->next = prev; prev = current; current = next; } /*ADD A STATEMENT HERE*/ } What should be added in place of “/*ADD A STATEMENT HERE*/”, so that the function correctly reverses a linked list.

• A. *head_ref = prev;
• B. *head_ref = current;
• C. *head_ref = next;
• D. *head_ref = NULL;