During which seasons do most stable radon levels occur?

The option indicating late Fall and early Spring as the seasons during which stable radon levels occur is accurate due to several factors related to building ventilation and the physics of radon gas.

Radon, a naturally occurring radioactive gas that can enter homes through cracks in floors, walls, and foundations, is influenced by both temperature and humidity. During late Fall and early Spring, external temperatures are colder, causing homeowners to keep windows and doors closed more frequently. This closed environment minimizes air exchange with the outside, leading to more stable, and often higher, indoor radon levels since the gas can accumulate without being diluted by outside air.

In contrast, summer often brings warmer temperatures and the use of air conditioning, which can alter ventilation patterns and allow for more air exchange, potentially lowering indoor radon levels. Similarly, during winter, heating systems might cause air to circulate in a way that disrupts the accumulation of radon, as homes can be ventilated differently depending on heating methods. Therefore, late Fall and early Spring are characterized by conditions that favor stable radon levels, making this choice the most fitting response to the question.