Which type of reaction produces the most harmful radiation ?

Answer: Option B

Radiation is one of the byproducts of radioactive decay of unstable atomic nuclei. Nuclear fission is the process on which the operation of most nuclear power plants is based. When certain nuclei (for example that of uranium-235) are bombarded with neutrons, the nucleus splits into two smaller nuclei of roughly (though not exactly) equal sizes. Because of the binding characteristics of the neutrons and protons in the original and resultant nuclei (and also the famous mass-energy relation that Einstein discovered), the result of this split is the liberation of a large amount of energy, manifested in the kinetic energy of the resultant nuclei.