The deviations from ideal gas depend on the temperature and pressure considered.

${\mathrm{NH}}_3$ will show maximum deviation from ideal gas due more to dipole -dipole attractions i.e. presence of hydrogen bonding which leads to more attractive forces between molecules of ${\mathrm{NH}}_3$ and therefore vander waal constants $\left(\mathrm{i}.\mathrm{e}. \mathrm{a}\&\mathrm{b}\right)$ are higher consequently ammonia is the one which shows the highest deviation under the same conditions among the given options.