The correct match is A-II, B-IV, C-I, D-III. Electron gain enthalpy is defined as the amount of energy released when an electron is added to an isolated gaseous atom. It increases from left to right in period. As we go down electronegativity becomes less negative. ‌F⟶−328kJ∕mol ‌Cl⟶−349kJ∕mol ‌O⟶−141kJ∕mol ‌S⟶−200kJ∕mol