有下列程序：
#include＜iostream＞
using namespace std;
class Complex

double re,im;
public:
Complex(double r,double i):re(r),im(i)
double real()constretum re;
double image()constreturn im;
Complex& operator+=(Complex

A．

re+=a.re;
im+=a.im;
return*this;

;
ostream& operator＜＜(ostream& s,const Complex& z)

return s＜＜’(’＜＜z.real()《’,’＜＜Z.image0＜＜’)’;

int main()

Complex x(1,2)，y(2,3);
cout＜＜(x+=y)＜＜endl;
return 0;

执行这个程序的输出结果是( )。A) (1,-2)
B．(2,3)
C．(3,5)
D．(3,1)