Which of the following requires a critical mass?

A) fission

B) gamma emission

C) beta emission

D) lepton

A) fission

Explanation:

Fission reactions require a critical mass. The critical mass is necessary because it makes a fission reaction self sustaining. This critical mass is the minimum amount of material required. Nuclear fission additionally depends on the composition, purity and concentration of the fissile material. Critical mass is important in the design of nuclear warheads.