Thus, the reactivity of nitrobenzene towards electrophilic aromatic substitution reaction is less.

Amino group is an electron releasing group. They increase the electron density on benzene ring.

Thus, aniline is more reactive towards electrophilic aromatic substituion reaction than benzene.

Hence, the correct order of reactivity towards the electrophilic substitution of the compounds, aniline $(I)$,benzene $(II)$,nitrobenzene $(III)$ is $I > II > III$.