b
(b) Halogens have very high electron affinity. It may be rated that the electron affinity of fluorine is unexpectedly low \(( < Cl)\). This may perhaps be due to small size of \(F\) atom. The value of electron gain enthalpies for \(Cl,\,F,\,S\) and \(O\) are respectively \(349, 333, 200\) & \(142 KJ / mol\) hence correct order is \(Cl > F > S > O\)