Concerning main propulsion reduction gears, what statement is true?

Correct Answer: Option A — The reduction gear allows the prime mover to rotate efficiently at relatively high-speed and low torque and allows the propeller to rotate efficiently at relatively low-speed and high torque.

Reduction gears facilitate efficient operation by matching the prime mover's high-speed, low-torque output to the propeller's requirement for low-speed, high-torque performance. This impedance matching ensures the engine operates within its optimal power curve while the propeller maintains efficient thrust production at lower rotational speeds.