Which of the following is the correct way to define the constructor(s) of the Sample class if we are to create objects as per the C#.NET code snippet given below?

Sample s1 = new Sample(); 
Sample s2 = new Sample(9, 5.6f);

public Sample()
{
    i = 0; 
    j = 0.0f;
}
public Sample (int ii, Single jj)
{
    i = ii;
    j = jj;
}

public Sample (Optional int ii = 0, Optional Single jj = 0.0f)
{
    i = ii;
    j = jj;
}

public Sample (int ii, Single jj)
{
    i = ii;
    j = jj;
}

Sample s;

s = new Sample();