Which one of the following radiations is most penetrating?

Gamma rays are the most penetrating form of radiation among the given options. This is due to their nature as high-energy electromagnetic waves, which allow them to pass through various materials with greater ease than other types of radiation.

Alpha rays consist of heavy helium nuclei that are relatively large and positively charged. Because of their size, they can be stopped by a sheet of paper or even the outer layer of human skin, making them the least penetrating.

Beta rays are electrons or positrons that are lighter than alpha particles. They have more penetrating power than alpha rays and can pass through materials like paper but are typically stopped by more dense materials such as plastic or aluminum.

X-rays are another form of electromagnetic radiation, but they have less energy than gamma rays. While they are capable of penetrating materials such as soft tissues in the human body, they do not have the same level of penetration power as gamma rays, especially when it comes to dense materials.

In summary, gamma rays stand out as the most penetrating type of radiation due to their high energy, which allows them to traverse materials with minimal attenuation, unlike alpha and beta particles and x-rays.