Interface ambiguous

class CustomCllection
    {
        C c1 = new XYZ();
        A a1 = new XYZ();
        B b1 = new XYZ();
        XYZ x = new XYZ();
        public void Check()
        {
            a1.i = 30;
            a1.Test1();
            a1.Test2();
            //-----------
            b1.k = 30;
            b1.Test2();
            b1.Test3();
            //----------------
            c1.i = 40;
            c1.k = 50;
            c1.m = 60;
            c1.Test1();
            c1.Test2(); // [Edit]Error is here
            c1.Test3();
            c1.Test4();
        }
    }
    interface A
    {
        void Test1();
        void Test2();
        int i { get;set;}
    }
    interface B
    {
        void Test2();
        void Test3();
        int k { get;set;}
    }
    interface C : B, A
    {
       new void Test3();
        void Test4();
        int m { get;set;}
    }
    class XYZ : C
    {
        public void Test1()
        {
            MessageBox.Show("Hello I am Test1");
        }
        void A.Test2()
        {
            MessageBox.Show("Hello I am Test2(A)");
        }
        void B.Test2()
        {
            MessageBox.Show("Hello I am Test2(B)");
        }
        public void Test3()
        {
            MessageBox.Show("Hello I am Test3");
        }
        public void Test4()
        {
            MessageBox.Show("Hello I am Test4");
        }
        int nn = 10;
        public int i
        {
            set { value = nn; }
            get { return nn; }
        }
        int nm = 10;
        public int m
        {
            set { value = nm; }
            get { return nm; }
        }
        int km = 10;
        public int k
        {
            set { value = km; }
            get { return km; }
        }

    }