下面程序的结果是 ______。
#include＜iostream.h＞
class A
public:
virtual void fun()=0;
;
class B:public A
public:
void fun () cout＜＜ "new file" ;
;
class C: public A
public:
void fun ()cout＜＜"open file"＜＜ " "
;
class D: public A
public:
void fun () cout＜＜ "save file\n" ;
;
void main()
A a,*p;
B b;
C c;
D d;
p=&c;
p-＞fun ();
p=&b;
p-＞fun ();
p=&d;
p-＞fun();

A．new file open file save file

B．new file new file new file

C．编译出错

D．open file new file save file