Which of the following statements are correct?

1. A switch statement can act on numerical as well as Boolean types.
2. A switch statement can act on characters, strings and enumerations types.
3. We cannot declare variables within a case statement if it is not enclosed by { }.
4. The foreach statement is used to iterate through the collection to get the desired information and should be used to change the contents of the collection to avoid unpredictable side effects.
5. All of the expressions of the for statement are not optional.

1. A class
2. A property
3. A struct
4. A function
5. An interface

class Sample
{
    int i;
    Single j;
    double k;
    public Sample (int ii, Single jj, double kk)
    {
        i = ii;
        j = jj;
        k = kk;
    } 
}

namespace CuriousTabConsoleApplication
{ 
    class SampleProgram
    {
        static void Main(string[] args)
        { 
            int num = 1;
            funcv(num); 
            Console.Write(num + ", "); 
            funcr(ref num); 
            Console.Write(num + ", ");
        }
        static void funcv(int num)
        { 
            num = num + 10; Console.Write(num + ", ");
        }
        static void funcr (ref int num)
        { 
            num = num + 10; Console.Write(num + ", ");
        } 
    } 
}

1. true
2. false
3. new
4. ~
5. sizeof