Vinegar owes its sour taste to acetic acid, which is not among the three named, so the answer is “None of these” — option 4.

What vinegar is. Vinegar is a dilute solution of acetic acid, CH₃COOH, usually 4 to 8 per cent by volume in water, produced by the bacterial oxidation of ethanol :

\(\text{C}_{2}\text{H}_{5}\text{OH}+\text{O}_{2}\xrightarrow{\ \text{Acetobacter}\ }\text{CH}_{3}\text{COOH}+\text{H}_{2}\text{O}\)

A 5 to 8 per cent solution of pure acetic acid in water is sold as vinegar; the pure acid, which freezes just below room temperature into ice-like crystals, is called glacial acetic acid.

Where the three named acids actually occur. This is the table the question is really testing :

Why the answer is an option-of-exclusion. The question is designed so that a candidate who knows only that vinegar is acidic will pick whichever acid sounds most familiar. The safe method is to identify the acid first — acetic — and only then look at the list. Since it is absent, “None of these” must be right.

Uses of vinegar follow from its acidity: it is a preservative, because most spoilage bacteria cannot grow at low pH; it is used in pickling, in salad dressing, and as a mild descaling agent for the calcium carbonate deposits in kettles.

Hence, the answer is None of these.