People use ordinary energy, and their sources are

The photosynthesis of plants changes solar energy into chemical energy, while coal, oil and the like are all evolved from animals and plants; For hydroelectric power generation, the source is also solar energy, which turns water into steam, and then liquefies into small water droplets at high altitude, that is, clouds form, which fall to the ground to form rain, and the rain merges into rivers, which in turn drives the turbine to generate electricity due to the kinetic energy of the river. Therefore, their roots are all from solar energy.

Therefore, A.