下列程序的输出结果是【 】。 include using namespace std; class Base{ int x; public: Base(int b):x(b){} virtual void display(){cout$amp; }; class Derired:public Base{ int y; public: Derived(int d):Base(d),y(d){} void display(){cout$amp; }; int main(){ Base b(1);Derived d(2); Base*p=&d; b.display();d.display();p->display(); return 0; }