Hi!
The correct option is D. Vitamin C.
Vitamin C, or more commonly ascorbic acid, is considered a weak sugar acid that is widely available in fruits and vegetables. It is structurally related to glucose, and has the molecular formula of C6H8O6, and is the only acidic substance of the options.
Baking Soda contains sodium bicarbonate which dissolves in water to yield a basic solution.
Antacids may be aluminium hydroxide or sodium bicarbonate that react with acids to neutralize the pH. Antacids are normally used to neutralize the pH of the stomach in people with stomach ulcers.
Ammonia (NH3) is essentially considered a weak base, which dissolve in water to yield hydroxide ions and ammonium ions.
Hope this helps!