Final answer:
The energy transformation involved in generating electricity at a hydroelectric power station is mechanical energy to electrical energy.
Step-by-step explanation:
The energy transformation involved in generating electricity at a hydroelectric power station is option A) Mechanical energy to electrical energy.
Hydropower is produced by converting the gravitational potential energy of falling or flowing water into kinetic energy and then into work to run electric generators or machinery. In a hydroelectric power station, the water stored behind a dam contains potential energy, which is converted into kinetic energy as the water rushes down. The kinetic energy is then used to turn the blades of turbines, causing a generator to generate electricity.