Identifying the structure of ethanoic anhydride

Steps:

• Recall ethanoic anhydride's formula: (CH₃CO)₂O, with two acetyl groups linked by an oxygen.
• Examine the diagram for a central O atom bonded to two C=O groups, each with CH₃ attached.
• Verify the molecular formula matches C₄H₆O₃.
• Confirm no other functional groups like alcohols or carboxylic acids are present.

Why A is correct:

• Option A depicts the exact anhydride structure with the (CH₃C=O)₂O linkage, matching the IUPAC definition of an acid anhydride.

Why the others are wrong:

• B shows a carboxylic acid (CH₃COOH), which has an OH group instead of the anhydride linkage.
• C represents an ester (e.g., CH₃COOCH₃), with an alkoxy group rather than symmetric acyl-oxygen-acyl.
• D illustrates ethanoic acid dimer or incorrect bonding, violating the anhydride's planar carbonyl arrangement.

Not enough information on exact diagram details, but based on standard structure.

Final answer: A