单项选择题

有以下程序:
#include <iostream>
#include <string>
using namespace std;
class Y;
class X

private:
int x;
char *strx;
public:
X(int a, char *str)

x=a;
strx=new char[strlen(str)+1];
strcpy(strx,str);

void show(Y &ob) ;
;
class Y

private:
int y;
char *stry;
public:
Y(int b,char *str)

y=b;
stry=new char[strlen(str)+1];
strcpy(stry, str);

friend void X: :show(Y &ob) ;
;
void X: :show(Y &ob)

cout<<strx<<", ";
cout<<ob, stry<<end1;

int main ( )

X a(10,"X");
Y b (20, "Y");
a. show(B) ;
return 0;

执行后的输出结果是( )。

A.X,Y
B.a,b
C.X,X
D.Y,Y