The element having very high ionization enthalpy but zero electron gain enthalpy is :

The correct option is D $He$
The element having very high ionization enthalpy but zero electron gain enthalpy is $He.$ The electronic configuration of $He$ is $1s^2$. It has completely filled $s$ subshell.
When an electron is removed from completely filled orbital, a large amount of energy is required. Hence, $He$ has very high ionization enthalpy. Since $He$ has completely filled valence shell, it is little or no tendency to accept an electron. Hence, $He$ is zero electron gain enthalpy.