static void Main(string[] args)
{
son s = new son();
Console.WriteLine(s.hello());
//////////////////////////////////
grandfather g = new son();
Console.WriteLine(g.hello());
}
static void Main(string[] args)
{
son s = new son();
Console.WriteLine(s.hello()); // call Son.hello()
//////////////////////////////////
grandfather g = s;
Console.WriteLine(g.hello()); // call Grandfather.hello()
Console.WriteLine(g.GetType());
}