What will be the Correct statement in the following C# code?

class sample
{
    protected int index;
    public sample()
    {
        index = 0;
    }
}
class sample 1: sample
{
    public void add()
    {
        index += 1;
    }
}
class Program
{
    static void Main(string[] args)
    {
        sample 1 z = new sample 1();
        z . add();
    }
}

A. Index should be declared as protected if it is to become available in inheritance chain

B. Constructor of sample class does not get inherited in sample 1 class

C. During constructing an object referred to by z, Firstly constructor of sample class will be called followed by constructor of sample 1 class

D. All of the mentioned

Answer: Option D