The set representing the correct order of ionic radius is:

Ionic radius trends:Increases down a group (due to additional shells).Decreases across a period (due to increasing effective nuclear charge).Comparing:${\text{Na}}^{+}$ ($n=2$) is larger than ${\text{Li}}^{+}$ ($n=1$).${\text{Mg}}^{2+}$ is smaller than ${\text{Na}}^{+}$ (isoelectronic, but ${\text{Mg}}^{2+}$ has higher $Z$).${\text{Li}}^{+}$ is larger than ${\text{Mg}}^{2+}$ is a common diagonal relationship comparison, but specifically: ${\text{Na}}^{+}(102\text{pm})>{\text{Li}}^{+}(76\text{pm})>{\text{Mg}}^{2+}(72\text{pm})>{\text{Be}}^{2+}(45\text{pm})$.Order: ${\text{Na}}^{+}>{\text{Li}}^{+}>{\text{Mg}}^{2+}>{\text{Be}}^{2+}$.