Concept:The correct preposition is used to show a comparison between two similar things.Explanation:The sentence compares Yusuf’s eloquence with his master’s eloquence.In standard English, the pair "compare with" is used when pointing out similarities or differences between two people or things.The completed sentence is: "Though Yusuf is a much younger lawyer, you cannot compare his eloquence with his master's."The other options ("by", "from", "for") do not fit the grammatical pattern of "compare".Answer:B. with