Which compound exhibits maximum dipole moment among the following?

The dipole moment ($$\mu$$) of a disubstituted benzene is the vector sum of the individual bond dipoles.

$$-NH_2$$ (Amino group): An electron-donating group (EDG) that pushes electron density toward the ring (dipole vector points toward the ring).

$$-NO_2$$ (Nitro group): An electron-withdrawing group (EWG) that pulls electron density away from the ring (dipole vector points away from the ring)

In p-nitroaniline, the $$-NH_2$$ group pushes electrons into the ring at one end, and the $$-NO_2$$ group pulls them out at the opposite end. Both vectors point in the same direction. Hence, has the highest dipole moment.