下列友元函数的定义中,错误的是( )。
A、class ABC{private: int x, y;public: ABC(int a=0, int b=0) { x = a; y = b; }friend void Show(ABC obj);};void Show(ABC obj) { cout
B、class ABC{friend void Show( ABC );private: int x, y;public: ABC(int a=0, int b=0) { x = a; y = b; }};void Show(ABC obj) { cout
C、class ABC{private: int x, y;public: ABC(int a=0, int b=0) { x = a; y = b; }friend Show( );};void Show(ABC obj) { cout
D、class ABC{private: int x, y;public:ABC(int a=0, int b=0) { x = a; y = b; }friend void Show(ABC obj) { cout << obj.x << obj.y; }};