Explanation:
An acidic salt is a salt that is formed from the partial neutralization of an acid, resulting in a pH lower than 7. When an acid reacts with a base, a salt and water are formed. The salt can either be acidic, basic, or neutral depending on the strength of the acid and base used.

Carbonic Acid:
Carbonic acid is a weak acid that is formed when carbon dioxide dissolves in water. It can partially dissociate into hydrogen ions (H+) and bicarbonate ions (HCO3-). When carbonic acid reacts with a base, such as sodium hydroxide (NaOH), sodium bicarbonate (NaHCO3) is formed. This salt is considered neutral since it does not have any remaining acidic or basic properties.

Phosphoric Acid:
Phosphoric acid is a strong acid that can fully dissociate into three hydrogen ions (H+) and phosphate ions (PO4^3-). When phosphoric acid reacts with a base, such as sodium hydroxide (NaOH), sodium phosphate (Na3PO4) is formed. This salt is considered basic since it contains the hydroxide ion (OH-) from the base.

Hydrochloric Acid:
Hydrochloric acid is a strong acid that can fully dissociate into hydrogen ions (H+) and chloride ions (Cl-). When hydrochloric acid reacts with a base, such as sodium hydroxide (NaOH), sodium chloride (NaCl) is formed. This salt is considered neutral since it does not have any remaining acidic or basic properties.

Sulphuric Acid:
Sulphuric acid is a strong acid that can fully dissociate into two hydrogen ions (H+) and sulfate ions (SO4^2-). When sulphuric acid reacts with a base, such as sodium hydroxide (NaOH), sodium sulfate (Na2SO4) is formed. This salt is considered neutral since it does not have any remaining acidic or basic properties.

Conclusion:
Carbonic acid is the only option that does not form an acidic salt. It forms a neutral salt, sodium bicarbonate (NaHCO3), when it reacts with a base. The other options, phosphoric acid, hydrochloric acid, and sulphuric acid, all form salts that are either basic or neutral.