You are correct, the answer is C) Generators. Single-shaft gas turbines are commonly used as prime movers to drive electrical generators aboard ships. Their high power density, reliability, and low maintenance requirements make them well-suited for electrical power generation applications. The other options are incorrect because: A) Multi-screw ships typically use diesel engines or electric motors as prime movers, not gas turbines. B) Single-screw ships also generally use diesel engines, not gas turbines, as the main propulsion. D) Auxiliary power units are smaller, separate systems from the main propulsion, and are not the typical application for single-shaft gas turbines.