In which of the following process maximum energy is released

O_(g) + e^– → O^–_(g); EA₁ ;  energy released on addition of electron

O^-_(g) + e^– → O^–2_(g); EA₂ ; energy is required to avoid repulsions between added electron and existing electron.

S_(g) + e^– → S^–_(g) ; EA₁ ; energy released on addition of electron

S^-_(g) + e^– → S^–2_(g) ; EA₂ ; energy is required to avoid repulsions between added electron and existing electron.

Oxygen due to its small size and presence of lone pairs has lesser affinity towards electrons. thus its  electron gain enthalpy is abnormally low in fact least in the group.

Hence 'S' has highest EA, i.e. maximum energy is released.

Option(C) is the correct answer.