The correct answer is B) Medium-speed diesel. Medium-speed diesel engines typically operate with a geared-drive featuring a single reduction. This configuration is common for medium-speed diesel propulsion systems used on many commercial and government vessels, including those operated by the US Coast Guard. The single reduction gearing allows the diesel engine to run at its optimal speed while the propeller turns at a lower, more efficient speed. Slow-speed diesels use direct drive without a reduction gear. Steam turbines and gas turbines also typically use different propulsion configurations that do not involve a single reduction gearbox.