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 irnag() 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() return 0; 程序执行后的输出结果是( )。
A．6+6i
B．6+1i
C．1+6i
D．1+1i