Electron gain enthalpy is the amount of energy released when an element accepts an electron. The process is endothermic.\\\\(\ ext {Lesser the electronic repulsion faced by an electron to get occupied in the outermost shell higher the amount of }\\\\)\\\\(\ ext {energy released.}\\\\)On moving down the group, the electron gain enthalpy decreases from S to Po. Oxygen has an unexpectedly low value of electron gain enthalpy.Since oxygen is smaller in size than S, so incoming \\\\(e^-\\\\) on oxygen faces more electronic repulsion on oxygen outermost surface ( due to more \\\\(e^-\\\\) density) as a result electron affinity decreases.The increasing order of electron gain enthalpy with negative sign is \\\\(O (-141.4 kJ/mol) < Po (-174 kJ/mol) < Te (-190.0 kJ/mol) < Se (-195.5 kJ/mol) < S (-208.8 kJ/mol)\\\\) Hence the correct answer is 0.