单项选择题

以下程序执行结果是 ( )。
#include ＜iostream.h＞
class Base
public
virtual void fun() cout＜＜"B";
;
class Derived
public:
Derived() cout＜＜"D";
virtual void fun() Base::fun(); cout＜＜"C";
int main ()
Base *ptr;
Derived obj;
ptr=&obj;
p-＞fun ( );
return 0;