Concept:Stars generate energy by combining light atomic nuclei into heavier ones in a process called nuclear fusion.
Explanation:Inside a star's core, extreme temperature and pressure force light nuclei such as hydrogen to collide and merge.
This process produces a heavier nucleus, usually helium.
During fusion, a small portion of mass is lost and converted into a large amount of energy.
This energy release follows Einstein's relation
E=mc2.
The continual fusion reactions in the core produce the heat and light radiated by stars.
Nuclear fission splits heavy nuclei and radioactive decay involves spontaneous breakdown, but neither powers stars.
Answer:The correct option is C. Nuclear fusion.