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