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