Which of the following factors is important for radon entry into buildings?

Soil composition plays a crucial role in radon entry into buildings because it directly influences the concentration of radon gas that can be released from the ground. Radon is a naturally occurring radioactive gas produced from the decay of uranium found in soil, rock, and water. The type of soil, its porosity, and the presence of uranium-bearing minerals will affect the amount of radon that can be generated and subsequently migrate upwards into structures.

For example, rocky soils may have higher levels of uranium, thus producing more radon, whereas sandy soils might allow radon to escape more easily without concentrating within the building. As such, understanding soil composition is key for assessing the potential risk of radon levels in a given location and for implementing appropriate mitigation strategies.