2.1練習（一）：1．理解下面的程序，并在VC++6.0下運行查看結果，回答程序后面的問題。#include "iostream.h"class CBase{public:CBase(int a)? :a(a){}protected:void print(){? cout<<"a="<<a<<endl;}private:int a;};class CDerive : public CBase{public:void print(){? CBase::print();? cout<<"b="<<b<<endl;}private:int b;};void main(){CDerive d;d.print();CBase b;b.print();}問題一：以上程序有兩大錯誤，試指出來，并改正之？2．理解下面的程序，并在VC++6.0下運行查看結果，回答程序后面的問題。#include "iostream.h"class CBase{public:CBase(int a)? :a(a){? cout<<"base structure"<<endl;}~CBase(){? cout<<"base destructure"<<endl;}void print(){? cout<<"a="<<a<<endl;}protected:int a;};class CDerive : public CBase{public:CDerive(int a, int b,int c)? :CBase(a),b(b),c(c){? cout<<"derive structure"<<endl;}~CDerive(){? cout<<"derive destructure"<<endl;}void print(){? CBase::print();? cout<<"b.a="<<b.a<<endl;? cout<<"c="<<c<<endl;}private:CBase b;int c;};void main(){CDerive d(1,2,3); -----------------------------------------------------①d.print();}問題一：以上程序的輸出結果是什么，說明為什么？問題二：①處語句執行完后，d.b.a的值為多少？2.2練習（二）：1．定義點CPoint類作為基類，在此基礎上派生出直線CLine類和圓CCircle類，并要求基類和各派生類具有以下特點：a．CLine類含有計算直線長度和斜率的成員函數；b．CCircle類含有計算圓面積的成員函數。