🔬 Step 1: Initial Reaction Analysis

The starting material is a five-membered ring lactone.

• When treated with NaOH and H₂O, base hydrolysis occurs.
• Hydroxide ion attacks the ester’s carbonyl carbon.
• The lactone ring opens, forming a molecule with a carboxylate ion (-COO⁻) and a hydroxyl group (-OH) at opposite ends of a four-carbon chain.

⚗️ Step 2: Acidic Hydrolysis and Cyclization

• Acidic hydrolysis with heat converts the carboxylate into a carboxylic acid (-COOH).
• The resulting molecule has both a -COOH and -OH group separated by three carbons.
• Upon heating, intramolecular esterification (lactonization) occurs, producing a cyclic ester.
• Since the reactive groups are separated by four carbons, a five-membered ring lactone forms.

🧪 Step 3: Identifying the Major Product

Among the options:

• Option A: Starting five-membered lactone
• Option B: Six-membered ring with ketone and hydroxyl groups
• Option C: Five-membered lactone with a hydroxyl side chain
• Option D: Final five-membered ring lactone formed via esterification