c++程序查错

麻烦大家给我看一下,我真的找不出错误的原因了,我的编译器提示的错误是不能访问私有数据!
可我并没有定义私有啊!请高手帮忙看看,谢谢
#include<iostream>
#include<string>
using namespace std;
class Person
{
public:
    Person(string nam , char s , int a)
    {
        name=nam;
        sex=s;
        age=a;
    }
protected:
    string name;
    char sex;
    int age;
};

class Teacher :virtual public Person
{
public:
    Teacher(string nam , char s , int a , string t):Person(nam , s ,a)
    {
        title=t;
    }
protected:
    string title;
};

class Student :virtual public Person
{
    Student(string nam , char s , int a ,float sco):Person(nam , s, a)
    {
        score=sco;
    }
protected:
    float score;
};

class Graduate :public Teacher ,public Student
{
public:
    Graduate(string nam , char s , int a , string t , float sco , float w)
        :Person(nam , s ,a),Teacher(nam , s , a , t),Student(nam , s , a ,sco),wage(w)
    {
        
    }
    void show()
    {
        cout<<"name:"<<name<<endl;
        cout<<"age:"<<age<<endl;
        cout<<"sex:"<<sex<<endl;
        cout<<"score:"<<score<<endl;
        cout<<"title:"<<title<<endl;
        cout<<"wages:"<<wage<<endl;
    }
protected:
    float wage;
};

int main()
{
    Graduate grad("WangSiyang",'B',23,"assistant",90,500000);
    grad.show();
    return 0;
}