Periodic Table and Periodicity

The statement(s) that are correct about the species $\mathrm{O}^{2-}, \mathrm{F}^{-}, \mathrm{Na}^{+}$ and $\mathrm{Mg}^{2+}$. (A) All are isoelectronic (B) All have the same nuclear charge (C) $\mathrm{O}^{2-}$ has the largest ionic radii (D) $\mathrm{Mg}^{2+}$ has the smallest ionic radii Choose the most appropriate answer from the options given below :