Final answer:
Alpha particles have the lowest penetrating power among the radioactive decay particles.
Step-by-step explanation:
The radioactive decay particles with the lowest penetrating power are alpha particles (E)
Alpha particles have the least penetrating power because they are the largest and slowest emission. They can be blocked by a sheet of paper or a human hand. On the other hand, beta particles (D), gamma rays (C), and positrons (B) have higher penetrating powers compared to alpha particles.