Data Structure by Java . help me quickly please ..

25 in A Binary tree, this method finds? public int xx(node n){ if (n== null) return 0; if (n.left == null && n.right null) return 1; if (n.left null && n.right !=null) return (1 + xx(n.right)); if (n.left != null && n.right ==null) return (1 + xx(n.left)); else return (1 + xx(n.left) + xx(n.right)); 2 Points) None of the above the number of internal nodes the number of nodes that has left child The number of external nodes the number of nodes