运行以下C++代码，屏幕将输出“derived class”。
#include <iostream>using namespace std; class base {public: virtual void show() { cout << "base class" << endl; }}; class derived : public base {public: void show() override { cout << "derived class" << endl; }}; int main() { base* b; derived d; b = &d; b->show(); return 0;}