The process that is NOT endothermic in nature is :
A. Ar₍₎ + e⁻ --> Ar⁻₍₎
B. H₍₎ + e⁻ --> H⁻₍₎
C. O⁻₍₎ + e⁻ --> O²⁻₍₎
D. Na₍₎ --> Na⁺₍₎ + e⁻