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

#include<iostream.h> 
struct MyStructure
{
    class MyClass
    {
        public:
        void Display(int x, float y = 97.50, char ch = 'a')
        {
            cout<< x << " " << y << " " << ch;
        }
    }Cls; 
}Struc;
 
int main()
{
    Struc.Cls.Display(12, 'b');
    return 0; 
}

#include<iostream.h> 
class TestDrive
{
    int x; 
    public:
    TestDrive(int xx)
    {
        x = xx;
    }
    int DriveIt(void);
};
int TestDrive::DriveIt(void)
{
    static int value = 0;
    int m;
    m = x % 2;
    x = x / 2;
    if((x / 2)) DriveIt(); 
    value = value + m * 10; 
    return value;
}
int main()
{
    TestDrive TD(1234);
    cout<< TD.DriveIt() * 10 << endl;
    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>
double CuriousTabFunction(double, double, double = 0, double = 0, double = 0);
int main()
{
    double d = 2.3;
    cout<< CuriousTabFunction(d, 7) << " ";
    cout<< CuriousTabFunction(d, 7, 6) << endl;
    return 0; 
}
double CuriousTabFunction(double x, double p, double q, double r, double s)
{
    return p +(q +(r + s * x)* x) * x;
}

#include<iostream.h> 
int main()
{
    int x = 10;
    int &y = x;
    x++;
    cout<< 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 x = 10;
    int &y = x;
    x = 25;
    y = 50;
    cout<< x << " " << --y;
    return 0; 
}