执行下面的程序将输出( ) class Base { public: Base(int n):c(n) { } void display() { cout << c << " "; } private: int c; }; class Derived : public Base { public: Derived(int n):Base(n+1),d(n) { } void display() { Base::display(); cout << d << endl; } private: int d; }; int main() { Derived d(1); d.display(); }