Which of the following is a common characteristic of drainage systems?

A common characteristic of drainage systems is that they are designed to facilitate flow using gravity, known as a gravity-driven flow design. This design relies on the natural force of gravity to move water and waste through pipes and other components, guiding them toward a disposal point, such as a sewer or a septic system. Utilizing gravity is efficient and helps minimize the need for pumps, which can be costly and require additional maintenance.

While other choices mention resistance to flow, venting systems, and specific usage in commercial buildings, these factors do not apply universally across all drainage systems. For instance, many residential and commercial drainage systems could be open or closed, can have varying resistance based on their design, and are not confined to a single type of building. Therefore, the emphasis on gravity-driven flow highlights a fundamental aspect that is common across a wide range of drainage systems.