13. Consider the following code snippet:

public class Demo 

{ 

 public static void main(String[] args) 

 { 

 Point[] p = new Point[4]; 

 p[0] = new Colored3DPoint(4, 4, 4, Color.BLACK); 

 p[1] = new ThreeDimensionalPoint(2, 2, 2); 

 p[2] = new ColoredPoint(3, 3, Color.RED); 

 p[3] = new Point(4, 4); 

 for (int i = 0; i < p.length; i++) 

 { 

 String s = p[i].toString(); 

 System.out.println("p[" + i + "] : " + s); 

 } 

 return; 

 } 

} 

This code is an example of ____. 

a) overloading

b) callback

c) early binding

d) polymorphism