如下程序声明了一个二维图形类TwoDShape，从其派生出矩形类Rec。 #include＜iostream＞ #include＜string＞ using namespaee std, class TwoDShape{// 二维图形类 char name[20]; public: TwoDShape (char * n="unknown") { strcpy(name, n); } Char * getName(){return name;} =0; }; class Rec: public TwoDShape{ double width, height public: Rec(double w-=0. 0,double h=0. 0):TwoDShape("rectangle") { width=w; height=h; } double getWidth() {return width;} double getHeight() {return height;} double area() {return width * height;} }; int main() { TwoDShape * shape; Shape=new Rec(2.1,3.0); cout＜＜"object is"＜＜shape-＞getName()＜＜"\n"; cout＜＜"Area is"＜＜shape-＞area()＜＜"\n"; return 0 } 请将程序补充完整，使程序在运行时输出： abject is triangle Area is 6.3