Which of the devices listed is commonly used to compensate for the expansion and minor misalignments occurring between the main turbine rotor and the reduction gear?

Correct Answer: Option D — Gear type flexible coupling

Gear-type flexible couplings utilize internal and external meshing teeth with crowning to accommodate unavoidable angular and parallel misalignments caused by hull flexing and thermal expansion between high-temperature steam turbine rotors and main reduction gears.