请看代码，回答下面的问题。

Type

TMammal=Class

Procedure Walk;

…..

end;{end of TManmml}

procedure TMammal.Walk;

begin

ShowMessage(‘Result is Mammal Walk’);

end;

TDog=Class(TMammal)

Procedure Walk;

end;

procedure TDog.Walk;

begin

ShowMessage(‘Result is Dog Walk’);

end;

var

Mammal:TMammal;

dog:TDog;

begin

Mammal:=TDog.Create;

Mammal.Walk;

Mammal.Free;

end;

上面代码中，最后的输出结果是：（ ）

A．‘Result is Dog Walk’

B．‘Result ia Mannal Walk’