How does the sun release nuclear energy?

A) Through the fusion of a uranium nucleus into smaller nuclei.
B) Through the fusion of hydrogen nuclei into a heavier nucleus.

Which feature of nuclear fission reactions allows these reactions to take place in a chain reaction?

A) Thermal energy is released and heats up the reactants.
B) More smaller atoms form that can undergo fission.
C) A larger atom is formed, which can then be split.
D) Neutrons start the reaction and are released during it.