The correct answer is A) Regenerative braking. When an AC synchronous electric propulsion motor driving a fixed-pitch propeller needs to reverse direction, the motor is electrically braked using a process called regenerative braking. In this process, the motor is temporarily used as a generator, converting the mechanical energy of the spinning shaft into electrical energy, which is then fed back into the power system. This electrical braking action slows down the motor before the shaft reverses direction, providing a smooth, controlled transition. The other options are incorrect because they do not accurately describe the braking process used in this situation. Dynamic braking, torsional braking, and friction braking are different techniques that are not typically employed for this type of motor reversal scenario on a vessel with an AC synchronous electric propulsion system.