关于C++的虚继承问题

第56行和第71行，为啥两个类的构造器可以继承Person的构造器，不是只有类才可以继承吗？难道是为了给name赋值吗？而且菱形继承，不是只需要继承中间那两个吗，为啥还把基类继承了？？所以，为啥92行代码（以及上面那样最后的逗号）去掉后，编译无法通过呢？？

#include <iostream>
#include <string>

class Person
{
public:
    Person(std :: string theName);

    void introduce();

protected:
    std::string name;
};

class Teacher : virtual public Person
{
public:
    Teacher(std::string theName, std::string theClass);

    void teach();
    void introduce();

protected:
    std::string classes;
};

class Student : virtual public Person
{
public:
    Student(std::string theName, std::string theClass);

    void attendClass();
    void introduce();
protected:
    std::string classes;
};

class TeachingStudent : public Student, public Teacher
{
public:
    TeachingStudent(std::string theName, std::string classTeaching, std::string classAttending);
    
    void introduce();
};

Person::Person(std::string theName)
{
    name = theName;
}

void Person::introduce()
{
    std::cout << "大家好，我是" << name << ".\n\n";
}

Teacher::Teacher(std::string theName, std::string theClass) : Person(theName)
{
    classes = theClass;
}

void Teacher::teach()
{
    std::cout << name << "教" << classes << ".\n\n";
}

void Teacher::introduce()
{
    std::cout << "大家好，我是" << name << "，我在" << classes << "学习.\n\n";
}

Student::Student(std::string theName, std::string theClass) : Person(theName)
{
    classes = theClass;
}

void Student::attendClass()
{
    std::cout << name << "加入" << classes << "学习.\n\n";
}

void Student::introduce()
{
    std::cout << "大家好，我是" << name << "，我在" << classes << "教书.\n\n";
}

TeachingStudent::TeachingStudent(std::string theName,
    std::string classTeaching,
    std::string classAttending)
    :
    Teacher(theName, classTeaching),
    Student(theName, classAttending),
    Person(theName)
{
}

void TeachingStudent::introduce()
{
    std::cout << "大家好，我是" << name << "，我教" << Teacher::classes << "，";
    std::cout << "同时我再" << Student::classes << "学习.\n\n";
}

int main(void)
{
    Teacher teacher("小甲鱼", "C++入门班");
    Student student("小乌龟", "C++入门班");
    TeachingStudent teachingstudent("小鱼儿", "C++入门班", "c++进阶班");

    teacher.introduce();
    teacher.teach();
    student.introduce();
    student.attendClass();
    teachingstudent.introduce();
    teachingstudent.teach();
    teachingstudent.attendClass();

    return 0;
};

56和71的写法不叫继承，是子类构造函数调用基类构造函数的一种写法