Which of the following systems uses a stack vent to function properly?

A venting system is essential for maintaining proper airflow within plumbing systems, allowing for the efficient removal of sewer gases and preventing the creation of a vacuum that can disrupt drainage. A stack vent functions as a vertical pipe that allows air to enter the plumbing system and helps maintain atmospheric pressure. This is crucial for ensuring that wastewater can flow smoothly down the drains without obstruction.

In a venting system, the stack vent connects to the drainage system, allowing air to move freely and preventing siphoning of the traps, which could lead to odor problems or drain backups. Proper venting is vital for any drainage system as it enhances the overall performance and hygiene of plumbing fixtures.

The other options, while related to plumbing, do not specifically require a stack vent to function properly. The drainage system deals with the removal of wastewater, the sewage system refers to a broader infrastructure for disposing of sewage, and the soil system pertains to the type of material or foundation in which pipes are laid, none of which inherently depend on a stack vent in the same way a venting system does.