The correct answer is A) Convert the kinetic energy of the steam exiting the nozzle to mechanical energy of rotation. The moving blades on a steam turbine are designed to capture the high-velocity steam exiting the turbine nozzles and convert that kinetic energy into mechanical rotation of the turbine shaft. As the steam flows over the curved surfaces of the moving blades, it causes the blades and the attached shaft to spin, generating the mechanical power that can then be used to drive other machinery. The other answer choices are incorrect because they do not accurately describe the primary function of the moving blades. Options B and D are incorrect as the blades do not convert potential energy or change the direction of the steam flow, but rather harness the kinetic energy. Option C is incorrect as the nozzles, not the moving blades, are responsible for changing the direction of the steam.