The set representing the correct order of ionic radius is:

Alkali metal ions have higher ionic radii than alkaline earth metal ions from the same time period.
Additionally, when we proceed through a period, the ionic radius both grows down the group and drops.
Thus, the ionic radii should be in the following order: ${\mathrm{Na}}^{+}>{\mathrm{Li}}^{+}>{\mathrm{Mg}}^{2+}>{\mathrm{Be}}^{2+}$

Hence, option (B) is correct.