47. 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 _________.

A cross-compound turbine features high- and low-pressure turbines on separate shafts, both driving a common reduction gear with steam flowing in series. This configuration aligns with the question's description of separate shafts and series steam flow.