Answer:
Nuclear energy
Step-by-step explanation:
There are many sources of energy available in nature which are harnessed by humans for their use. Some of these sources are present in abundant quantity (solar energy) while others take million of years to renew (coal and petroleum).
Nuclear energy is generated when two nuclei fuse into a larger nuclei (nuclear fusion) or a large nuclei dissociates into smaller ones (nuclear fission) .
A small quantity of nuclear fuel produces a large amount of energy. It is difficult to control the energy production process on which chemist hve worked. Also, the disposal of radioactive waste produced was also a challenge.