单项选择题
有如下程序：
#include
using namespace std;
class Point{
public:
Point(int xx=0,int yy=0):x(xx),y(yy) { }
protected:
void SetXY(int xx,int yy) { x=xx; y=yy; }
private:
int x,y;
};
class Circle:public Point{
public:
Circle(int r):radius(r) { }
void Set(int r,int x,int y) { radius=r; SetXY(x,y); } //①
void Print() const { cout<
A．①
B．②
C．③
D．④
