Given below is the Node class to perform basic list operations and a Stack class with a no arg constructor.
Select from the options the appropriate pop() operation that can be included in the Stack class. Also 'first' is the top-of-the-stack.

class Node
{
	protected Node next;
	protected Object ele;
	Node()
	{
		this(null,null);
	}
	Node(Object e,Node n)
	{
		ele=e;
		next=n;
	}
	public void setNext(Node n)
	{
		next=n;
	}
	public void setEle(Object e)
	{
		ele=e;
	}
	public Node getNext()
	{
		return next;
	}
	public Object getEle()
	{
		return ele;
	}
}
 
class Stack
{
	Node first;
	int size=0;
	Stack()
	{
		first=null;
	}
}

A.

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		Object o = first.getEle();
		first = first.getNext();
		size--;
		return o;
	}
}

B.

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		Object o = first.getEle();
		first = first.getNext().getNext();
		size--;
		return o;
	}
}

C.

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		first = first.getNext();
		Object o = first.getEle();
		size--;
		return o;
	}
}

D.

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		first = first.getNext().getNext();
		Object o = first.getEle();
		size--;
		return o;
	}
}

Answer: Option A