写出下列程序运行的结果。
public abstract class A
{
public A()
{
Console.Write('A');
}
public virtual void Fun()
{
Console. Write("A.Fun()");
}
}
public class B : A
{
public B()
{
Console.Write('B');
}
public override void Fun()
{
Console.Write("B.Fun()");
}
public static void Main()
{
A a = new B();
Console.WriteLine();
a.Fun();
}
}