Which of the following would react most readily with nucleophiles?

Step-by-step solution

Nucleophile always attacks on electron deficient site. Presence of electron withdrawing group such as NO ₂, CHO etc., decreases the electron density on benzene nucleous, hence such group activates the ring towards nucleophilic attack. While presence of electron releasing groups such as R or O R increase the electron density, thus deactivate the nucleus toward nucleophilie attack. NO ₂ group activate the ring more than Cl toward nucleophilic attack hence react readily with nucleophile.