Cl atom has the highest electron affinity in the periodic table. F is a member of group 17 has highest electron gain enthalpy than S which is a group 16 element. This is turn is higher than the electron affinity of O atom. Thus,

Cl > F > S > O

For isoelectronic species, ionic radius increases when there is increase in negative charge. It happens because effective nuclear charge on the atom (Z_eff) decreases.

Same when ionic radius decreases with increase in positive charge as Z_eff increases.

Among the given options (a), (c) and (d), the option (d) has the highest ionisation energy because of extra stability associated with half-filled 3p-orbital. In option (b), the presence of 3d¹⁰ electrons offers shielding effect, as a result the 4p³ electrons do not experience much nuclear charge and hence the electrons can be removed easily.

Going from left to right across a period in the periodic table, the basicity decreases as the electronegativity of the atom possessing the lone pair of electron increases. Hence basicity of $$NH_2^-$$ is higher than F^-. In moving down a group, as the atomic mass increases, basicity decreases. Hence F^- is more basic than I^- and HO^- is more basic than HS-. Hence among the ionic species, $$NH_2^-$$ has maximum proton affinity.