下列程序的输出结果是【 】。 #include<iostream> using namespace std; class base{ public: int n; base (int x){n=x;} virtual void set (int m){n=m;cout<<n<<;} }; class deriveA:public base{ public: dericeA(int x):base(x){} void set(int m){n+m;cout<<n<<’’’’;} }; Class deriveB:public base{ public: deriveB(int x):base(x){} void set(int m){n+m;cout<<n<<’’’’;} }; int main() { deriveA d1(1); deriveB.d2(3); base*pbase; pbase=&d1; pbase->set(1); pbase=&d2; pbase->set(2); return 0; }