{"knowledge_schema": {"broad_category": "Chemistry \u2192 Organic Chemistry \u2192 Reaction Mechanisms", "refinement": "This problem involves understanding the stereochemistry of organic compounds and the effects of different reducing agents on these compounds during chemical reactions.", "specific_scope": "The focus is on identifying the correct starting materials (C and D) for two reactions that yield specific stereoisomers of 3-methyl-4-oxopentanoic acid after reduction.", "goal": "Determine the appropriate starting materials for the reactions based on the products formed and the stereochemistry involved."}, "summary": "This problem is rooted in organic chemistry, specifically in the area of reaction mechanisms and stereochemistry. It requires identifying the correct starting materials for two reactions that produce different stereoisomers of 3-methyl-4-oxopentanoic acid when treated with different reducing agents. The goal is to analyze the reactions and their products to deduce the correct identities of the starting materials, leading to the conclusion that C is (S)-3-methyl-4-oxopentanoic acid."}