What type of gas could be drawn out by a proper ventilation system in basements?

Radon gas is the correct answer because it is a naturally occurring radioactive gas that can accumulate in enclosed spaces such as basements. It is produced from the natural breakdown of uranium in soil, rock, and water, and can seep into homes through cracks in floors and walls, construction joints, and gaps around service lines. Proper ventilation systems are crucial in basements to dilute and remove radon gas, thereby reducing the risk of exposure to harmful levels.

Ventilation helps in maintaining air quality by ensuring a continuous exchange of indoor and outdoor air, which can effectively lower radon levels. Testing for radon is recommended in homes, especially those built on or near radon-prone areas.

The other gases listed may have specific health or safety concerns, but they do not typically accumulate in basements in the same way that radon does. Carbon dioxide is a normal component of indoor air and is not hazardous in low concentrations. Methane is primarily a concern in areas near gas leaks or agricultural waste, and nitrous oxide is generally found in emissions rather than within the confines of a basement environment.