Which of the following statement is correct about the program given below?

#include<iostream.h> 
class CuriousTab
{
    int x, y; 
    public:
    CuriousTab(int xx = 0, int yy = 0)
    {
        x = xx; 
        y = yy;
    }
    void Display()
    {
        cout<< x << " " << y;
    }
    CuriousTab operator +(CuriousTab z)
    {
        CuriousTab objTemp;
        objTemp.x = x + z.x;
        objTemp.y = y + z.y;
        return objTemp; 
    }
};
int main()
{
    CuriousTab objCuriousTab1(90, 80); 
    CuriousTab objCuriousTab2(10, 20); 
    CuriousTab objSum; 
    CuriousTab &objRef = objSum; 
    objRef = objCuriousTab1 + objCuriousTab2; 
    objRef.Display(); 
    return 0; 
}

#include<iostream.h> 
struct Tab
{
    short n;
};
int main()
{
    Tab b;
    Tab& rb = b;
    b.n = 5;
    cout << b.n << " " << rb.n << " ";
    rb.n = 8;
    cout << b.n << " " << rb.n;
    return 0; 
}

#include<iostream.h> 
enum xyz
{
    a, b, c
};
int main() 
{
    int x = a, y = b, z = c;
    int &p = x, &q = y, &r = z;
    p = ++x;
    q = ++y;
    r = ++c;
    cout<< p << q << r;
    return 0;
}

#include<iostream.h> 
int x, y; 
class CuriousTabTest
{
    public:
    CuriousTabTest(int xx = 0, int yy = 0)
    {
        x = xx;
        y = yy;
        Display(); 
    } 
    void Display()
    {
        cout<< x << " " << y << " ";
    }
};
int main()
{
    CuriousTabTest objBT(10, 20); 
    int &rx = x; 
    int &ry = y; 
    ry = x;
    rx = y;
    cout<< rx--; 
    return 0; 
}

#include<iostream.h> 
class CuriousTab
{
    int x, y; 
    public:
    void SetValue(int &xx, int &yy)
    {
        x =  xx++;
        y =  yy; 
        cout<< xx << " " << yy;
    }
};
int main()
{
    int x = 10;
    int &y = x;
    CuriousTab objCuriousTab;
    objCuriousTab.SetValue(x , y);
    return 0; 
}

#include<iostream.h> 
class CuriousTabBase
{
    int x;
    public:
    CuriousTabBase(int xx = 0)
    {
        x = xx; 
    }
    void Display()
    {
        cout<< x ;
    }
};
class CuriousTabDerived : public CuriousTabBase
{
    int y; 
    public:
    CuriousTabDerived(int yy = 0)
    {
        y = yy;
    }
    void Display()
    {
        cout<< y ;
    }
};
int main()
{
    CuriousTabBase objBase(10); 
    CuriousTabBase &objRef = objBase;

    CuriousTabDerived objDev(20); 
    objRef = objDev;

    objDev.Display(); 
    return 0; 
}

#include<iostream.h> 
int main()
{
    int m = 2, n = 6;
    int &x = m;
    int &y = n;
    m = x++; 
    x = m++;
    n = y++;
    y = n++;
    cout<< m << " " << n; 
    return 0; 
}

#include<iostream.h> 
int i, j; 
class CuriousTab
{
    public:
    CuriousTab(int x = 0, int y = 0)
    {
        i = x; 
        j = x; 
        Display();
    }
    void Display()
    {
        cout<< j <<" ";
    } 
}; 
int main()
{
    CuriousTab objCuriousTab(10, 20); 
    int &s = i; 
    int &z = j; 
    i++;
    cout<< s-- << " " << ++z; 
    return 0; 
}

#include<iostream.h> 
class CuriousTab
{
    int x, y; 
    public:
    CuriousTab(int &xx, int &yy)
    {
        x = xx;
        y = yy;
        Display();
    }
    void Display()
    {
        cout<< x << " " << y;
    }
};
int main()
{
    int x1 = 10; 
    int &p = x1;
    int y1 = 20; 
    int &q = y1; 
    CuriousTab objCuriousTab(p, q); 
    return 0; 
}

#include<iostream> 
enum curioustab
{
    a=1, b, c
};
int main()
{
    int x = c;
    int &y = x;
    int &z = x;
    y = b;
    std::cout<< z--;
    return 0; 
}

#include<iostream.h> 
class CuriousTab
{
    int x, y; 
    public:
    void SetValue(int &a, int &b)
    {
        a = 100;
        x = a;
        y = b;
        Display();
    }
    void Display()
    {
        cout<< x << " " << y; 
    }
};
int main()
{
    int x = 10;
    CuriousTab objCuriousTab;
    objCuriousTab.SetValue(x, x);
    return 0;
}