The correct order of reactivity towards the electrophilic substitution of the compounds aniline (I), benzene (II) and nitrobenzene (III) is

The reactivity of compounds towards electrophilic substitution is determined by the electron-donating or electron-withdrawing nature of the substituents present on the benzene ring.

1. Aniline (I) has an -NH2 group attached to the benzene ring. The -NH2 group is a strong electron-donating group. It increases the electron density on the benzene ring, making it more reactive towards electrophilic substitution.

2. Benzene (II) has no substituent groups, so its reactivity is standard.

3. Nitrobenzene (III) has a -NO2 group attached to the benzene ring. The -NO2 group is a strong electron-withdrawing group. It decreases the electron density on the benzene ring, making it less reactive towards electrophilic substitution.

Therefore, the correct order of reactivity towards electrophilic substitution is Aniline (I) > Benzene (II) > Nitrobenzene (III).