Alkyl halides are more reactive towards nucleophilic substitution. Reactivity depends upon the stability of carbocation intermediate formed.
Among the given halides aryl halide is least towards nucleophile as in it the C-X bond acquire some double bond character due to resonance.
Presence of electron withdrawing groups like -NO2 at ortho and para position facilitate the nucleophilic displacement of -X of aryl halide.
Among the alkyl halide, 3o are more reactive than 2o alkyl halides due to the formation of the more stable carbocation.
Hence the order of reactivity of C-X bond towards nucleophile is as follows: