Which system is the CO connected to?

The correct choice indicates that the CO, which stands for Carbon Monoxide, is connected to the Sanitary Sewer system. This connection is critical in understanding how carbon monoxide, which can be a byproduct of incomplete combustion from heating appliances, must be safely disposed of to protect public health and the environment.

When a building uses combustion appliances like furnaces or water heaters, the carbon monoxide produced should be vented properly to prevent hazardous buildup indoors. In this context, the sanitary sewer system is designed to handle waste and can include components that address gas emissions in ways that minimize health risks. Proper venting systems are essential to ensure that gases do not contribute to environmental pollution or pose a danger to inhabitants.

The other systems mentioned provide key functions but do not have the same direct relationship with the management of carbon monoxide emissions. The freshwater supply is dedicated to providing clean water, storm drainage systems manage surface water runoff, and heating systems focus on maintaining temperature control, each serving their distinct purposes without direct involvement in the safe disposition of carbon monoxide.