参考前面内容声明Teacher(教师)类，声明Professor(教授)类，是Teacher(教师)类的派生类，新增私有成员projects（项目）,另声明类BirthDate(生日)包含year , month , day等数据成员和display函数，生日信息作为Professor类的一个数据成员，并且在Professor中提供一个修改生日的成员函数，在主函数中创建Professor对象，修改生日，并输出其Professor对象所有数据成员。

下面是对应的C++代码实现：

#include <iostream>
using namespace std;

class BirthDate {
public:
    int year;
    int month;
    int day;
    void display() {
        cout << year << "-" << month << "-" << day << endl;
    }
};

class Teacher {
public:
    string name;
    int age;
    string gender;
    Teacher(string n, int a, string g) : name(n), age(a), gender(g) {}
    void display() {
        cout << "Name: " << name << endl;
        cout << "Age: " << age << endl;
        cout << "Gender: " << gender << endl;
    }
};

class Professor : public Teacher {
private:
    string projects;
    BirthDate birthday;
public:
    Professor(string n, int a, string g, string p, BirthDate b) : Teacher(n, a, g), projects(p), birthday(b) {}
    void setBirthday(int y, int m, int d) {
        birthday.year = y;
        birthday.month = m;
        birthday.day = d;
    }
    void display() {
        Teacher::display();
        cout << "Projects: " << projects << endl;
        cout << "Birthday: ";
        birthday.display();
    }
};

int main() {
    BirthDate bday = {1990, 7, 1};
    Professor p("Tom", 30, "Male", "AI Research", bday);
    p.display();
    cout << "After modifying the birthday: " << endl;
    p.setBirthday(1985, 1, 15);
    p.display();
    return 0;
}

运行结果：

Name: Tom
Age: 30
Gender: Male
Projects: AI Research
Birthday: 1990-7-1
After modifying the birthday: 
Name: Tom
Age: 30
Gender: Male
Projects: AI Research
Birthday: 1985-1-15