Give reasons: The presence of nitro group (-NO2) at ortho/para positions increases the reactivity of haloarenes towards nucleophilic substitution reaction.

This is because the nitro group (-NO2) at o/p positions withdraws electrons from the benzene ring, which facilitates the attack of the nucleophile. The negative charge in the carbanion formed at o/p positions with respect to the halogen atom is stabilized by the presence of nitro groups (-NO2) and resonance, respectively.