单选题 有如下程序:
#include ＜iostream＞
using namespace std;
class Base{
public:
void output() { cout＜＜1; }
virtual void Print() { cout＜"B"; }
};
class Derived:public Base{
public:
void output() { cout＜2;}
void Print() { cout＜＜"D"; }
};
int main() {
Base *ptr=new Derived;
ptr-＞output();
ptr-＞Print();
delete ptr;
return();
}
程序的输出结果是