A turbine assembly in which steam flows in series through a high pressure turbine and then on to a low pressure turbine, with both turbines driving a common reduction gear through separate shafts, is classified as _________.

Correct Answer: Option D — cross-compound

A cross-compound turbine configuration divides expansion between independent high-pressure and low-pressure units operating in series. Each turbine drives the main reduction gear via separate pinions and shafts, optimizing thermal efficiency and accommodating high enthalpy drops.