Which of the following statements are correct about an interface used in C#.NET?

1. An interface can contain properties, methods and events.
2. The keyword must implement forces implementation of an interface.
3. Interfaces can be overloaded.
4. Interfaces can be implemented by a class or a struct.
5. Enhanced implementations of an interface can be developed without breaking existing code.

1. int[] a = {25, 30, 40, 5};

2. int[] a;
   a = new int[3];
   a[0] = 25;
   a[1] = 30;
   a[2] = 40;
   a[3] = 5;

3. int[] a;
   a = new int{25, 30, 40, 5};

4. int[] a;
   a = new int[4]{25, 30, 40, 5};

5. int[] a;
   a = new int[4];
   a[0] = 25;
   a[1] = 30;
   a[2] = 40;
   a[3] = 5;

String s1 = "ALL MEN ARE CREATED EQUAL";
String s2;
s2 = s1.Substring(12, 3); 
Console.WriteLine(s2);

namespace CuriousTabConsoleApplication
{
    class SampleProgram
    {
        static void Main(string[ ] args)
        {
            int i = 10;
            double d = 34.340;
            fun(i);
            fun(d);
        }
        static void fun(double d)
        {
            Console.WriteLine(d + " ");
        }
    }
}

1. A Structure can be declared within a procedure.
2. Structs can implement an interface but they cannot inherit from another struct.
3. struct members cannot be declared as protected.
4. A Structure can be empty.
5. It is an error to initialize an instance field in a struct.