Answer: Option C
:
C
Generally, to determine whether energy is released or absorbed when an electron is added to a neutral gaseous atom, you need to look at the stability of the species.
If we add an electron to Cl atom, energy will be released because $C{l}^{-}$ is more stable than Cl atom.
If we add an electron to N atom, energy will be absorbed because N is more stable than $N^{-}$
In the case of anions, energy is always absorbed when an electron is added.
So, if an electron is added to $O^{-}$ ion a lot of energy is needed to make it$O^2-$