The correct option is D O2−>F−>Na+>Mg2+>Al3+
All the given species contains 10 e− each i.e. isoelectronic.
For isoelectronic species, anion having high negative charge is the largest in size and cation having high positive charge is the smallest in size.
So, the correct order is :
O2−>F−>Na+>Mg2+>Al3+