Which ordering of compounds is according to the decreasing order of the oxidation state of nitrogen?

Since the oxidation state of ${\mathrm{HNO}}_3,\mathrm{NO},{\mathrm{N}}_2$ and ${\mathrm{NH}}_4\mathrm{Cl}$ is +5, +2,0 and -3 respectively.

Hence the decreasing order of the oxidation state of nitrogen is, ${\mathrm{HNO}}_3,\mathrm{NO},{\mathrm{N}}_2,{\mathrm{NH}}_4\mathrm{Cl}$.