The correct option is:
Beta decay releases a particle, while gamma decay only reduces the energy level. Neither beta decay nor gamma decay is a form of nuclear fission.
In beta decay, a neutron in the nucleus is transformed into a proton, which results in the emission of a beta particle (electron or positron). In gamma decay, an excited nucleus releases energy in the form of gamma radiation without changing its number of protons or neutrons. Neither process is classified as nuclear fission, which specifically involves the splitting of a heavy nucleus into smaller nuclei.