单项选择题

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( )。

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