Chemistry - Aromatic Hydrocarbon Question with Solution | TestHub

Nitrobenzene shows $-\mathrm{M}$ effect.

In nitrobenzene, it is known that the nitro group is an electron-withdrawing species, and therefore, it comes under the category of deactivating species. Thus, it favours meta-position for the upcoming substitution in benzene ring since deactivating groups have higher electron density in meta position than ortho and para position.
Thus, the electrophilic substitution reaction for nitrobenzene is meta-directing.

Chlorobenzene shows $-\mathrm{I}$effect.

Cl shows a negative inductive effect due to its high electronegativity means it withdraws the electron density from the benzene ring, so it is a deactivating group.

The activation effect on substitution reaction shown by toluene is due to hyperconjugation. 

$-{\mathrm{CH}}_3$ shows $+\mathrm{M}$ and $+\mathrm{I}$.

Hence, order is B > A > C > D.