Final answer:
In the context of converting highly oxygenated biomass carbohydrates to hydroxyl-free fine chemicals via hydrogenation, the suitable metal catalyst from the given options is ruthenium (Ru).
Step-by-step explanation:
The conversion of highly oxygenated biomass carbohydrates into useful hydroxyl-free fine chemicals through hydrogenation typically uses certain metals as catalysts. While metals like platinum and palladium are traditionally used in hydrogenation reactions to add hydrogen across a multiple bond, the reaction condition for biomass conversion can be different and may require specific catalysts. Nickel is commonly used in the hydrogenation of polyunsaturated fats and oils to produce saturated fats and oils, as it helps mediate the reaction of compounds containing carbon-carbon double bonds with hydrogen.
However, when referring to the specific question about the conversion of highly oxygenated biomass carbohydrates into hydroxyl-free fine chemicals and the given options for metal catalysts (Pb, Li, Ru, Cr), the appropriate catalyst for this reaction is ruthenium (answer 'd. Ru'). Ruthenium catalysts are known for their effectiveness in various hydrogenation processes, including biomass conversion.