阅读下列C++程序和程序说明，将应填入(n)处的字句写在对应栏内。
【说明】Point是平面坐标系上的点类，Line是从Point派生出来的直线类。
include ＜iostream.h＞
class Point
{public:
Point (int x, int y) ;
Point (Point &p) ;
～Point();
void set (double x, double y) ;
void print();
private:double X,Y;
};
Point::Point (int x, int y) //Point 构造函数
{X=x; Y=y; }
Point::Point ((1) ) //Point 拷贝构造函数
{X=p.X; Y=p.Y；}
void Point::set (double x, double y)
{X=x; Y=y; }
void Point::print()
{cout＜＜' ('＜＜X＜＜","＜＜Y＜＜") "＜＜endl; }
Point::～Point()
{cout＜＜"Point 的析构函数被调用! "＜＜endl;
class Line: public Point
{public:
Line (int x, int y, int k) ;
Line (Line &s) ;
～Line();
void set (double x, double y, double k)
void print();
private:double K;
};
(2)//Line 构造函数实现
{ K=k;}
(3)//Line 拷贝构造函数实现
{K=s.K;}
void Line::set (double x, double y, double k)
{ (4);
K=k;
}
void Line::print()
{cout＜＜" 直线经过点";
(5);
cout＜＜"斜率为: k="＜＜K＜＜endl;
}
Line: :～Line()
{cout＜＜"Line 析构函数被调用! "＜＜endl;
}
void main()
{Line 11 (1,1,2) ;
11 .print();
Linel2 (11) ;
12.set (3,2,1) ;
12.print();
}