Which method is used to produce electricity in hydroelectric power plant?

The correct answer is: By running dynamo by kinetic energy

•  The production of electricity by the motion of water running through electrical generators is in simple terms is known as hydroelectric power. 
• The water is the energy medium in this case or the mass for the energy formula and when the water/mass which when fall on the turbine generator possess a potential energy which when falling on the generator is converted into kinetic energy, the kinetic energy which move the turbine or the wheels (structure of the turbine generator) of the electrical generator in turn converting mechanical energy (sum of potential and kinetic energy) into electrical energy.
•  When the water falls on the wheel at a certain velocity, most of the energy of the falling water is converted from potential energy to kinetic energy. 
• correct option is (C) as kinetic energy is needed to move the turbine at a certain speed to generate the electricity by overcoming the threshold conditions.