A common means of providing return air to the air handling unit in a commercial system is through which of the following?

The correct choice highlights that a common means of providing return air to the air handling unit in a commercial system is through the space above a suspended ceiling. This area is often utilized for several practical reasons. The space above a suspended ceiling typically acts as an effective plenum that allows for the balanced distribution of air throughout the building. It facilitates the return of air to the HVAC system efficiently, ensuring that cooled or heated air is recycled appropriately.

Utilizing this space can help maintain a more uniform temperature throughout the commercial space and enable better air quality management because it minimizes the need for extensive ductwork in the occupied space below. Another advantage is that it can also reduce noise levels within the occupied areas since the equipment can be positioned above the ceiling tiles.

The other mentioned options either do not provide efficient air return pathways or are less practical within a commercial setting, making them insufficient choices compared to utilizing the plenum space above the suspended ceiling.