The correct order of electron gain enthalpy is:

🧠 S beats O for electron gain — O's $2p$ orbital is too small, the new electron faces too much repulsion Same story as F vs Cl in halogens. The Period 2 element of any group that gains electrons (O, F) is unusually CRAMPED. Adding an extra electron to a tiny $2p$ shell raises repulsion. The Period 3 cousin (S, Cl) wins for electron gain enthalpy.

🗺️ Compare Group 16 values (kJ/mol) $\ce{S} = -200$ — most exothermic in this set. $\ce{Se} = -195$. $\ce{Te} = -190$. $\ce{O} = -141$ — anomalously LOW because of $2p$ repulsion.

Order by magnitude (most to least): S > Se > Te > O.

⚠️ The trap Option (b) puts O at the top: $\ce{O} > \ce{S} > \ce{Se} > \ce{Te}$. This is the "expected" group trend without applying the Period 2 anomaly. The smaller atom should win, students think — but for O, the smallness causes too much repulsion when an electron is added. Memorize: in both Group 16 and Group 17, the second-row element loses to its third-row cousin in $|\Delta_{eg}H|$.

$\boxed{\text{Answer: (c)}}$