Override/overload/interface combination test ~

The content is from. Net essence.CodeAs follows:
Public interface icommon {void doit ();}
Public class base: icommon {
Void icommon. doit () {();};
Public Virtual void doit () {B ();}
}
Public class derived: Base, icommon {
Void icommon. doit () {C ();}
Public new virtual void doit () {d ();}
}
Public class reallyderived: derived {
Public override void doit () {e ();}
}
Public static void main (){
Reallyderived R1 = new reallyderived ();
Derived r2 = R1;
Base R3 = R1;
Icommon r4 = R1;

R1.doit (); //
R2.doit (); // B
R3.doit (); // C
R4.doit (); // d
}

Which of the above four ABCD methods is called: {A (); B (); C (); D (); E?