A Stack Based on a Linked List Is Based on the Following

A stack based on a linked list is based on the following code
Class Node{
String element;
Node next;
Node(String el,Node n) {
Element = el;
Next = n;
}
}
Node top = null;
The code for implementing the String pop() operation is

A) if (top != null)
{
Top = top.next;
String el = top.element;
Return el;
}
Else throw new RuntimeException("Empty Stack") ;
B) if (top != null.
{
String el = top.element;
Top = top.next;
Return el;
}
Else throw new RuntimeException("Empty Stack".;
C) if (top != null.
{
String el = top.element;
Top = null;
Return el;
}
Else throw new RuntimeException("Empty Stack".;
D) return top.element;
Top = top.next;