若有以下程序: #include <iostream> using namespace std; class Base private: int a,b; public: Base(int x, int y) a=x; b=y; void show() cout<<a<<", "<<b<<end1; ; class Derive : public Base private: int c, d; public: Derive(int x,int y, int z,int m):Base(x,y) c=z; d=m; void show() cout<<c<<", "<<d<<end1; ; int main () Base b(50,50),*pb; Derive d(10,20,30, 40); pb=&d; pb->show (); return 0; 招待程序后的输出结果是( )。
A. 10,20
B. 30,40
C. 20,30
D. 50,50