Concept:Ethanoic acid is a two-carbon carboxylic acid. Its common name is different from its systematic IUPAC name.
Explanation:Ethanoic acid has the molecular formula
CH3COOH.
It contains a two-carbon chain, so its IUPAC name is ethanoic acid.
The common name for this same compound is acetic acid.
Acetic acid is the main component of vinegar.
It is widely used in food preservation and chemical production.
The other options are common names of different carboxylic acids: butyric acid has four carbons, propionic acid has three carbons, and formic acid has one carbon.
Therefore, ethanoic acid is correctly identified as acetic acid.
Answer:A. Acetic acid