The ionic radii $$(\mathop A\limits^o)$$ of $$\mathrm{C}^{4-}$$ and $$\mathrm{O}^{2-}$$ respectively are 2.60 and 1.40. The ionic radius of the isoelectronic ion $$\mathrm{N}^{3-}$$ would be

Assertion (A) Electron gain enthalpy becomes less negative as we go down a group.

Reason (R) Size of the atom increases on going down the group and the added electron would be farther away from the nucleus.