The electronic configuration of $\mathrm{Na}, \mathrm{Ne}, \mathrm{Mg}$ and $\mathrm{Al}$ after the removal of an electron is as
$\begin{aligned}
& \mathrm{Na}^{+}: 1 s^2, 2 s^2, 2 p^6 \\
& \mathrm{Ne}^{+}: 1 s^2, 2 s^2, 2 p^5 \\
& \mathrm{Mg}^{+}: 1 s^2, 2 s^2, 2 p^6, 3 s^1 \\
& \mathrm{Al}^{+}: 1 s^2, 2 s^2, 2 p^6, 3 s^2
\end{aligned}$
The ionisation energy decreases as the size of the atom/ion increases. Further ionisation energy increases with increase in nuclear charge.
Since, $\mathrm{Na}^{+}$gives a stable electronic configuration hence its $\mathrm{IE}_2$ is highest among the given species and therefore the correct order of their $\mathrm{IE}_2$ is
$\mathrm{Mg} < \mathrm{Al} < \mathrm{Ne} < \mathrm{Na}$