题目内容：

[单选题]有下列程序: include using namespace std; class Demo { public: Demo(){cout<<"d

有下列程序： #include＜iostream.h＞ using namespace std; class Demo { public: Demo(){ cout＜＜"default constmctor/n";} Demo(const Demo &x){ cont＜＜"copy constructor/n";} }; Demo userCode(Demo b){Demo c(b);return c;} int

A．1和1

B．1和2

C．2和3

D．2和4