What will happen when you compile and run the following code:

import java.util.Hashtable;

public class X extends String
{
    public int hashCode() {return 0;}

    public static void main(String argv[])
    {
        X x = new X();
        Hashtable h = new Hashtable();
        h.put("key", x);
        System.out.println(h.get("key"));
    }
}
A) Compilation error.
B) No ouput.
C) Output null
D) Output 0
E) Output key
F) Exception: "NullPointerException"