Hello! Remember you have to write complete questions in order to find good and exact answers. Here I'll assume that you need a relationship between D and N. So we know some facts:
So this is an inverse relationship. We can write this as:
[tex]D\propto \frac{1}{N} \\ \\ \\ \boxed{D=k\frac{1}{N}} \\ \\ \\ \text{Where k is a positive constant}[/tex]
Since N lies in the denominator, as it increases then D will decrease. So this is a correct relationship