(d)
Given, $z = i$
Let $z_{1} = 1 + i\left( 1 \pm \sqrt{3} \right)$ and $z_{2} = 2 + i$
Now, $\left| z_{2} - z \right| = |1 + i - i| = 2$
As we know that the distance from the centre to every vertices is equal
Now, $\left| z_{1} - z \right| = |1 + i\left( 1 \pm \sqrt{3} \right) - i|$
$= |1 \pm i\sqrt{3}|$
$= \sqrt{1^{2} + \left( \sqrt{3} \right)^{2}} = 2$