Radioisotopes often emit one or more types of radiation, including alpha particles, beta particles, and gamma rays. The distance the radiation travels through matter before being absorbed increases in order from alpha to gamma. Which statement describes the best radioisotope that can be used for radioisotope imaging and for radionuclide therapy?

It emits only gamma rays.
It emits only alpha particles.
It emits alpha and beta particles.
It emits beta particles and gamma rays.