Ester structure reveals alcohol type and ring geometry

Steps:

• Analyze Z's ester groups: the carbon attached to -O- in the alcohol part has two alkyl substituents, classifying X as secondary.
• Identify Y as a dicarboxylic acid with a flexible chain, making it non-planar in its reactive form.
• Observe Z's ring: formed by esterification, it adopts a puckered conformation due to bond angles, rendering it non-planar.
• Match these features to option A, confirming the double ester cycle.

Why A is correct:

• Secondary alcohol X forms esters where the -OH carbon bonds to two carbons, and non-planar Y (e.g., aliphatic chain) cyclizes to a non-planar ring in Z per standard cyclic ester geometry.

Why the others are wrong:

• B: Y is non-planar, not planar, as dicarboxylic acids lack aromatic rigidity.
• C: X is secondary, not tertiary (tertiary lacks H for esterification); Z ring is non-planar.
• D: X is secondary, not tertiary; Y is non-planar.

Final answer: A