单项选择题

如下程序的输出是
#include<iostream>
using namespace std;
class Base
public:
Base( )cout<<"BB";f( );
void f( )cout<<"Bf";

class Derived:public Base
public:
Derived( )eout<<"DD";
void f( )cout<<"Df";

int main( )Derived d;return 0;

A.BBBff)D
B.BBDfDDDf
C.DD
D.DDBBBf