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;
}
}