The correct answer is: B. Fission reaction.
A fission reaction is a nuclear reaction in which an atomic nucleus splits into two or more smaller nuclei. This process releases a large amount of energy, which can be used to generate electricity or create nuclear weapons.
Fission reactions can produce harmful radiation in the form of gamma rays and neutrons. Gamma rays are high-energy photons that can cause damage to DNA and other biological molecules. Neutrons can also damage DNA, and they can also interact with other atoms to produce radioactive isotopes.
Chemical reactions do not produce harmful radiation. Chemical reactions are changes in the composition of matter that do not involve changes in the nuclei of atoms.
Photochemical reactions are chemical reactions that are initiated by light. These reactions can produce harmful radiation if the light is of high enough energy. However, most photochemical reactions do not produce harmful radiation.
Therefore, the correct answer is: B. Fission reaction.