Esterification of carboxylic acid and alcohol Steps:

• Carboxylic acid C₃H₆O₂ corresponds to propanoic acid, CH₃CH₂COOH.
• Alcohol C₂H₆O corresponds to ethanol, CH₃CH₂OH.
• Esterification combines the acyl group from the acid (CH₃CH₂C=O) and alkyl group from the alcohol (CH₃CH₂), losing H₂O.
• Resulting ester structure is CH₃CH₂C(=O)OCH₂CH₃, matching option A.

Why A is correct:

• It is the structure of ethyl propanoate, formed by standard esterification where the acid contributes the carbonyl chain and alcohol the alkoxy group.

Why the others are wrong:

• B: Requires butanoic acid (C₄H₈O₂) and methanol (CH₄O), not matching given formulas.
• C: Structure of ethyl butanoate with C₆H₁₂O₂, exceeding combined carbons from reactants.
• D: Chemically identical to A but non-standard notation; however, A uses conventional acid-alkyl order.

Final answer: A