Question -
Answer -
Bio-mass is obtained from the dead plants and animals. It is a renewable source of energy. Examples of bio-mass sources of energies are wood, gobar-gas.
Hydroelectricity is obtained from the potential energy of the stored water at a certain height. Water from a certain height is made to fall on the turbines of the generator resulting in electricity. Dams and reservoirs are used in hydroelectricity.
Both bio-mass and hydroelectricity are renewable sources of energies.