To determine the electron-withdrawing nature of the given substrates, we need to analyze the effect of each group on the electron density of the molecule.

(a) -OH (Hydroxyl group):
The hydroxyl group is an electron-donating group due to the presence of a lone pair of electrons on the oxygen atom. This lone pair can donate electron density to the rest of the molecule, making -OH a weak electron-withdrawing group.

(b) -OCH3 (Methoxy group):
The methoxy group consists of an oxygen atom bonded to a carbon atom, which is further bonded to three hydrogen atoms. The oxygen atom in -OCH3 is more electronegative than carbon, resulting in a partial negative charge on oxygen. This partial negative charge withdraws electron density from the rest of the molecule, making -OCH3 an electron-withdrawing group.

(c) -SO3H (Sulfonic acid group):
The sulfonic acid group contains a sulfur atom bonded to three oxygen atoms, one of which is bonded to a hydrogen atom. The sulfur atom is highly electronegative and can withdraw significant electron density from the rest of the molecule. Therefore, -SO3H is a strong electron-withdrawing group.

(d) -ph (Phenyl group):
The phenyl group is a benzene ring bonded to a substituent. In this case, the substituent is not specified. However, the phenyl group itself is neither an electron-donating nor an electron-withdrawing group. The electron-withdrawing or donating nature of the substituent attached to the phenyl group will determine the overall effect on electron density.

In summary:
- (a) -OH is a weak electron-withdrawing group.
- (b) -OCH3 is an electron-withdrawing group.
- (c) -SO3H is a strong electron-withdrawing group.
- (d) -ph (phenyl group) itself is neither electron-withdrawing nor electron-donating. Its electron-withdrawing or donating nature depends on the substituent attached to it.

Overall, (c) -SO3H is the strongest electron-withdrawing group among the given options.

Option D phenyl group is electron withdrawing group