\((2)\) In a group, from top to bottom the basic nature increases that means acidic nature decreases.

\(Na, Mg\) and \(Al\) are present in same period so the order of basic nature among and \(Al\) is \(Na> Mg > Al.\)

And \(\mathrm{Na}\) and \(\mathrm{K}\) are from same group so basic nature of \(\mathrm{K}>\mathrm{Na}\).

So the correct order of oxides

\(\mathrm{Al}_{2} \mathrm{O}_{3}<\mathrm{MgO}<\mathrm{Na}_{2} \mathrm{O}<\mathrm{K}_{2} \mathrm{O}\)