Which of the following statements about alpha rays is true?

Alpha rays, or alpha particles, are indeed highly ionizing. This high ionization occurs because alpha particles are composed of two protons and two neutrons, making them relatively heavy compared to other forms of radiation, such as beta particles or gamma rays. Their substantial mass and positive charge lead to a greater likelihood of interacting with and disrupting atoms in the materials they pass through, effectively causing ionization.

In contrast to other types of radiation, alpha particles have limited penetration abilities. They can be stopped by just a few centimeters of air or a sheet of paper, making them less hazardous outside the human body. The statement regarding their speed is also misleading; alpha rays do not travel at the speed of light, as they are considerably slower due to their mass. Therefore, the characteristic of being highly ionizing is a distinguishing feature of alpha rays, highlighting why this statement is true.