Java Puzzle 13 (spot the bug if one exists)

Puzzle13.java

public class Puzzle13 {

	public static void main(String[] args){
		A b1 = new B();
		A c1 = new C();
		
		A b2 = b1;
		A c2 = c1;
		
		// what will get printed?
		b2.print(c2);
	}

	public static class A extends Object {
		public void print(A object) {
			System.out.println("An instance of " + object.getClass().getSimpleName() 
					+ " was passed to A's print(A object)");
		}
	}
	
	public static class B extends A {
		public void print(A object) {
			System.out.println("An instance of " + object.getClass().getSimpleName() 
					+ " was passed to B's print(A object)");
		}
	}
	
	public static class C extends B {
		public void print(A object) {
			System.out.println("An instance of " + object.getClass().getSimpleName() 
					+ " was passed to C's print(A object)");
		}
	}
	
	public static class D extends A {
		public void print(A object) {
			System.out.println("An instance of " + object.getClass().getSimpleName() 
					+ " was passed to D's print(A object)");
		}
	}
	
}