Gamma radiation can be shielded best by:

Gamma radiation is a type of electromagnetic radiation that is highly penetrating, meaning it can easily pass through most materials. To effectively shield against gamma radiation, dense materials with high atomic numbers are required, as they provide better absorption of the energy carried by gamma photons.

Lead is particularly effective as a shielding material because its high density and atomic number offer substantial resistance to gamma radiation. When gamma rays interact with lead, they are more likely to be absorbed or scattered, significantly reducing the intensity of the radiation that can pass through. This makes lead the preferred choice for constructing barriers in radiological facilities or during handling of radioactive materials.

In comparison, materials like paper or personal protective equipment (PPE) offer minimal protection against gamma radiation due to their low density and atomic structure. Water can provide some shielding effects, but it is less efficient than lead because it is not as dense. Therefore, lead is the optimal choice for effective gamma radiation shielding.