1. Study the following method carefully which can be related to a certain class, decide what does it do?

   public void Unknown(E item)

   {

   Node node = new Node(item);

   Node parent=null, current;

   char d;

   if(root == null)

   root = node;

   else

   {

   current = root;

   while(current != null)

   {

   parent = current;

   if (current.data < item)

   { current = current.right;

   d=r; }

   else

   { current = current.left;

   d=l;

   }

   }

   if(d==l)

   parent.left = node;

   else

   parent.right = node;

   }

   }

   	a.	Insert a node in a binary search tree with item as its data
   	b.	Remove a node which its data is equal to item from a binary tree
   	c.	Insert a node in a binary tree with item as its data
   	d.	Remove a node which its data is equal to item from a binary search tree