The strongest acid from the following is

In the case of substituted phenols, the acidity of phenols increases in the presence of the electron-withdrawing group. This is due to the stability of the phenoxide ion generated. In case of meta substituted phenols, the acidic nature can be explained on the basis of inductive effect. Among the given groups $-{\mathrm{NO}}_2 \& -\mathrm{Cl}$ groups are electron withdrawing groups and methyl group is electron releasing group.

Acidic strength order is :