Which of the following best describes a market maker?

A market maker is best described as a trader who holds physical inventory to quote prices. This role is crucial in ensuring liquidity in the market by being ready to buy and sell commodities at specified prices. By maintaining an inventory, the market maker can respond to buyer and seller interest effectively, thereby facilitating smoother trading conditions.

Holding physical inventory allows market makers to manage supply and demand fluctuations, which is essential for stabilizing prices. This ability to quote prices continuously helps create a more efficient marketplace, as it provides participants with a reliable way to execute their trades promptly.

The other options depict roles that do not encompass the full responsibilities of a market maker. For instance, a trader who only trades commodities for clients does not inherently provide the liquidity or price quoting that a market maker does; rather, they are more akin to an agent for the client's interests. A salesperson who manages risk for clients implies a focus on advisory roles without engaging in active trading or market-making functions. Lastly, a broker facilitating trades between buyers and sellers does not typically take on the inventory risk associated with being a market maker, as brokers enable transactions but do not maintain their own inventory for the purpose of quoting prices.