In which of the following, elements are arranged in the correct order of their electron gain enthalpies.

We know that the electron gain enthalpy increases from left to right and decreases from top to bottom. So here, Fluorine has maximum electron gain enthalpy. Now in $2^{\mathrm{nd}}$ period size of elements are too small so inter-electronic repulsion is maximum and due to this reason it is slightly difficult to add the electron in elements of $2^{\mathrm{nd}}$ group therefore after fluorine sulphur have higher electron gain enthalpy. Hence, the final order will be:

$\mathrm{F}>\mathrm{S}>\mathrm{O}>\mathrm{N}$