Q.The element with positive electron gain enthalpy is :

Electron gain enthalpy is the energy change when an atom gains an electron; it is positive (energy must be supplied) for atoms that resist accepting an electron. …

The question asks which element has a positive electron gain enthalpy, i.e. releases no energy (rather absorbs energy) when it gains an electron.

Electron gain enthalpy (ΔH_eg) is the enthalpy change when a gaseous atom accepts an electron to form a negative ion. For most non-metals it is negative (energy is released). It becomes positive (energy has to be supplied) when the atom is already very stable and does not want an extra electron. …