As there is resonance involved, we can say the methoxy group is ortho para directing. But due to presence of oxygen atom there is strong negative inductive effect which takes the electron density from the benzene ring, even so the net result is activation of ring.

Chlorobenzene shows the same resonance effect as the first compound but the negative effect is less pronounced since oxygen has a higher electronegativity than Chlorine. So the net activation of benzene ring is less effective than anisole (methoxybenzene).

Nitrobenzene is strongly deactivating and meta directing group as shown in the above figure, there is positive charge developed at ortho and para position so electrophilic substitution becomes less probable.

So the reactivity of electrophilic substitution reaction is based on the above arguments is: