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();

}