Cardiac Pacemakers Once Used Plutonium-238 as a Power Source

Cardiac pacemakers once used plutonium-238 as a power source. Plutonium-238 decays by the emission of gamma rays and alpha particles. This emission is not particularly harmful because __________.

A) gamma rays are not absorbed very strongly by biological tissue, and alpha particles do not penetrate beyond the container.
B) gamma rays and alpha particles are the least dangerous form of radiation.
C) gamma rays and alpha particles do not penetrate beyond the container.
D) gamma rays are absorbed by the container, and alpha particles do not affect biological tissue.