阅读以下说明和C++程序，将入(n)处的字句写在答题纸的对应栏内。 说明 以下程序的功能是计算三角形、矩形和正方形的面积并输出。 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()，作为计算上述三种图形面积的通用接口。 c++程序 include ＜iostream.h＞ inclule ＜math.h＞ class Figure { public: virtual double getArea()= 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 ='lb; this-＞lc = lc; } double getArea() { double s = (la+lb+lc)/2.0; return sqrt(s*(s-la)*(s-lb)*(s-lc)); } }; void main() { Figure* figures[3] = { new Triangle(2,3,3), new Rectangle(5,8), new Square(5)}; for (int i = 0; i ＜ 3; i++) { com ＜＜ 'figures[' ＜＜ i ＜＜ '] area =' ＜＜ (figures[i])-＞getArea0 ＜＜ endl; }