Given below are two statements $:$
Statement $(I) :$ The radii of isoelectronic species increase in the order $Mg^{2+} < Na^{+} < F^{-} < O^{2-}$.
Statement $(II) :$ The magnitude of electron gain enthalpy of halogens decreases in the order $Cl > F > Br > I$.
In the light of the above statements,choose the most appropriate answer from the options given below $:$

• A
  Statement $I$ is incorrect but Statement $II$ is correct
• B
  Both Statement $I$ and Statement $II$ are incorrect
• C
  Statement $I$ is correct but Statement $II$ is incorrect
• D
  Both Statement $I$ and Statement $II$ are correct