Implementing the Interface

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C#

Below codes are exactly from book example. But still giving me errors. I couldn't figure out what is wrong. Book also gave the output: Baby is called: kitten and Baby is called: puppy. I have hard time understanding the interface, on top of that this book example is giving me error, any help will be very appreciated.

{
    interface ILiveBirth
    {
        string BabyCalled();
    }
    class Animal { }
    class Cat : Animal, ILiveBirth
    {
        string ILiveBirth.BabyCalled()
        { return "kitten"; }
    }
    class Dog : Animal, ILiveBirth
    {
        string ILiveBirth.BabyCalled()
        { return "puppy"; }
    }
    class Bird : Animal
    { }

    class Program
    {
        static void Main()
        {
            Animal[] animalArray = new Animal[3];
            animalArray[0] = new Cat();
            animalArray[1] = new Bird();
            animalArray[2] = new Dog();
            foreach(Animal a in animalArray)
            {
                ILiveBirth b = a as ILiveBirth;
                if (b ! = null)
                Console.WriteLine("Baby is called:{0}", b.Babycalled());
            }
        }
    }
}