protected member OOP question

[StGuru]

I got one question about protected members.

Here is the code:

#include <iostream>

using namespace std;

class osnovna
{
      protected:
      
      int test;
      
};

class izvedena : private osnovna
{

public:

       void funkcija()
       {
           cin>>test;
           
           cout<<test;
       }

};

class izvedena1 : public izvedena
{
      
      public:

      void tesit()
      {
           cin>>test;
           
           cout<<test<<endl;
      }
};
      
int main()
{

    izvedena dva;
    
    dva.funkcija();
    
    system("PAUSE");

    return 0;
    
}

Why when I write izvedena : public osnovna, or izvedena : protected osnovna the izvedena1 class can access the variable test and with private not?

Can somebody elaborate please?

Thanks in advance.