Answer: a blacktop highway
A stem cell is a cell that has layers of bacteria that helps protect the water that follows through it.
Solar energy is energy that comes from the sun and is captured by solar cells. These cells transform the energy of photons of light into electrical energy. One mechanism is the energization of electrons, here the energy of the photons is transferred to the electrons, which can already be considered electric energy.
As for the hydroelectric energy, here the waterfalls or rivers flow driving a turbine, which will transform the movement into usable electric energy as it rotates.
Autotrophs are organism that is a Heterotroph.
