The correct order of reactivity towards the electrophillic...

Nitro group $\left(-\mathrm{NO}_2\right)$ is an electron withdrawing group. It removes electron density from aromatic nucleus. Thus, the reactivity of nitrobenzene towards electrophilic aromatic substitution reaction is less. Amine group $\left(-\mathrm{NH}_2\right)$ 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 is. aniline $($\mathrm{I}$)>$ benzene (II) $>$ nitrobenzene (III).