In the operation of a marine propulsion gas turbine, kinetic and thermal energy required to drive the main propeller shaft are extracted by which of the following?

Correct Answer: Option D — Power turbine.

The power turbine is the component responsible for extracting the remaining kinetic and thermal energy from the high-velocity gas stream exiting the gas generator. This energy is converted into mechanical torque, which is then transmitted through the power turbine shaft to the reduction gear and the main propeller shaft.