单选题 有以下程序：
#include＜iostream＞
using namespace std;
class Complex
{
public:
Complex(double r=0,double i=0):re(r),im(i){}
double real() const{return re;}
double imag() const{return im;}
Complex operator+(Complex c)const
{return Complex(re+c.re,im+c.im);}
private:
double re,im;
};
int main()
{
Complex a=Complex(1,1)+Complex(5);
cout＜＜a.real()＜＜"+"＜＜a.imag()＜＜"i"＜＜endl;
return 0;
}
程序执行后的输出结果是______。