Consider the following abstract class declaration.

public abstract class 2DShape
{
abstract public double getArea();
public String toString()
{ return A shape with area getArea(); }
}

Which of the following class declarations correctly extend the abstract class 2DShape?

I.
public class Circle extends 2DShape
{
double r;
// constructors not shown
public double getArea()
{ return 3.14 * r * r; }
public String toString()
{ return "A circle with radius " + r; }
}
II.
public class Triangle extends 2DShape
{
double b;
double h;
// constructors not shown
public double getArea()
{ return b * h / 2; }
}
III.
public class Polygon extends 2DShape
{
int numSides;
// constructors not shown
public int getArea()
{ return numSides; }
public String toString()
{ return "A polygon with " + numSides + " sides."; }
}

A. I, II and III
B. I and II only
C. II only
D. I and III only
E. I only