An optically active compound A, C6H10O2, when dissolved in NaOH solution, consumed one equivalent of base. On acidification, compound A was slowly regenerated. Treatment of A with LiAlH4 in ether followed by protonolysis gave an optically inactive compound B that reacted with acetic anhydride to give an acetate diester derivative C. Compound B was oxidized by aqueous chromic acid to ?-methylglutaric acid (3-methylpentanedioic acid), D. Identify compounds A, B, and C; do not specify stereochemistry. (The absolute stereochemical configurations of chiral substances cannot be determined from the data.)