The correct relation between electron gain enthalpy $(Δ_\mathrm{eg}H)$ and electron affinity $A_\mathrm{e}$ at any temperature '$T$' is
A) $Δ_\mathrm{eg}H = -A_\mathrm{e} - \frac{5}{2}RT$
B) $Δ_\mathrm{eg}H = \frac{A_\mathrm{e}}{RT}$
C) $Δ_\mathrm{eg}H = \frac{-A_\mathrm{e}}{RT}$
D) $Δ_\mathrm{eg}H = \frac{-A_\mathrm{e}}{RT} + \frac{1}{A_\mathrm{e}^2}$
I have read that electron affinity could be taken as electron gain enthalpy at absolute zero, i.e. 0 K. So, maybe we could use Kirchoff's law for temperature $T$, but why is $C_p$ taken and not $C_v$ or something else, is it from the definition?