In which of the following options order of arrangement does not agree with the variation of property indicated against it ? A) $A{l}^{3+}<M{g}^{2+}<N{a}^{+}<F^{-}$ (increasing ionic size) B)$B<C<N<O$ (increasing first ionisation enthalpy) C)$I<Br<Cl<F$ (increasing electron gain enthalpy) D)$Li<Na<K<Rb$ (increasing metallic radius)

First ionisation energy is the energy required to remove an electron from outermost shell.
Hence , correct order is $B<C<O<N$
For option (b)
Electron gain enthalpy is the energy required to gain an electron in the outermost shell.ltbegt Hence , the correct order is $I<Br<F<CI$
For option (c)
As we move down the group in alkali metal , metallic radius increases $Li<Na<K<Rb$
For option (d)
In case of isoelectronic species increases the ionic size of the species increases and vice-versa
$Al<M{g}^{2+}<N{a}^{+}<F^{-}$