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】

以下C++程序的功能是计算三角形、矩形和正方形的面积并输出。程序由4个类组成：类Triangle、Rectangle和Square分别表示三角形、矩形和正方形；抽象类Figure提供了一个纯虚拟函数getArea()，作为计算上述3种图形面积的通用接口。

include＜iostream.b＞

include＜math.h＞

class Figure{

public:

virtual double getArea0=0; //纯虚拟函数

};

class Rectangle: (1) {

protected:

double height;

double width;

public:

Rectangle(){};

Rectangle(double height, double width){

This-＞height=height;

This-＞width=width;

}

double getarea(){

return (2);

}

};

class Square: (3) {

public:

Square(double width){

(4);

}

};

class Triangle: (5) {

double la;

double lb;

double lc;

public:

Triangle(double la, double lb, double lc){

this-＞la=la; this-＞lb; this-＞lc;

}

double getArea(){

double s=(la+lb+lc)/2.0;

return sqrt(s*(s-la)**(s-lb)*(s-lc));

}

};

viod main(){

Figure* figures[3]={

new Triangle(2,3,3), new Rectangle(5,8), new Square(5));

for(int i=0;i＜3;i++){

cout＜＜"figures["＜＜i＜＜"]area="＜＜(figures[i])-＞getarea()＜＜endl;

}

}