In a hydro power plant, (a) Potential energy possessed by stored water is converted into electricity.
Explanation: Hydropower plants utilize the potential energy stored in water at high elevations, which is converted to kinetic energy as the water flows down, then that kinetic energy is used to spin a turbine which generates electricity.
Why other options are incorrect:
(b) Kinetic energy possessed by stored water is converted into potential energy:
This is the reverse process of what happens in a hydropower plant. Water flowing down gains kinetic energy, but the hydro plant converts the potential energy of the stored water (at high elevation) into electricity.
(c) Electricity is extracted from water:
While the process involves converting water’s stored energy into electricity, it’s not as if electricity is directly “extracted” from the water.
(d) Water is converted into steam to produce electricity:
Steam power plants use steam to drive turbines and generate electricity, but this is not the process in a hydropower plant. Hydropower plants use the direct conversion of water’s potential energy to electricity.