The following function reverse$()$ is supposed to reverse a singly linked

list. There is one line missing at the end of the function.

$/*$ head$\_$ref is a double pointer which points to head pointer

of linked list $*/$

static void reverse$($Node head$\_$ref$)\{$

Node prev $=$ null;

Node current $=$ head$\_$ref;

Node next;

while $($current $$ null$)\{$

next $=$ current.next;

current.next $=$ prev;

prev $=$ current;

current $=$ next;

$\}$

$/`$ADD A STATEMENT HERE$*/$

$\}$

A$.$ head$\_$ref$=$ current;

B$.$ head$\_$ref$=$ prev;

C$.$ head$\_$ref $=$ null;

D$.$ head$\_$ref$=$ next;