The organic acid present in vinegar is
A.Methanoic acid
B.Ethanoic acid
C.Propanoic acid
D.None of these

Hint: We know that vinegar is composed of Acetic and water. Keeping in mind the composition of vinegar we can move forward to answer this question.

Step by step answer:
Acetic acid is a carboxylic acid also known as ethanoic acid. Vinegar is a solution of approximately 5% concentrated acetic acid diluted by water. Vinegar is produced by fermentation and oxidation of natural carbohydrates.
The ethan- in ethanoic acid means the compound has a double bond which denotes it has two carbon atoms as $\left( {C = C} \right)$.
 The –oic acid part in the end of ethanoic acid means that the carbon on the end is a part of a carboxylic acid group ${\text{ }}COOH$. The Chemical formula for ethanoic acid is $C{H_3}COOH$.
Acetic acid is an acid because it has acidic properties. The presence of ${\text{ }}COOH$ group also known as carboxylic acid group is solely responsible for the acidic nature.
It is a weak acid because it partially dissociates in aqueous solution. The hydrogen centre in the carboxyl group (${\text{ }}COOH$) in carboxylic acids can separate from the molecule by ionization:
$C{H_3}COOH \to C{H_3}CO{O^ - } + {H^ + }$
This release of a proton (${H^ + }$), brings acidic character to acetic acid. Acetic acid is a weak monoprotic acid.
Therefore, we conclude that Option B is the correct option.

Note: Ethanoic acid is a valid IUPAC name for acetic acid according to the nomenclature of the compound $C{H_3}COOH$. The name acetic acid is derived from the Latin word “acetum”, meaning vinegar. Glacial acetic acid is the name for the acetic acid that is non-diluted or without water in it. It can also be called anhydrous acetic acid.