What refers to the spaces between studs in a wall used as air plenums?

The correct choice identifies the spaces between the studs in a wall that serve a specific purpose in the building's mechanical system. These cavities, referred to as studwall cavities, are integral in routing air for heating, ventilation, and air conditioning (HVAC) systems.

When walls are constructed, the vertical framing members, or studs, create enclosed spaces that can hold insulation, wiring, and sometimes ductwork. In many applications, particularly in residential and commercial buildings, these cavities are utilized as air plenums. This functionality is crucial for distributing conditioned air throughout a space, allowing for efficient temperature control and air flow.

The term "studwall cavities" accurately captures the nature of these spaces as they are both enclosed by the wall itself and formed by the framing members. Other terms provided, while they might relate to air movement or ventilation in a broader sense, do not specifically define the structural elements as effectively as "studwall cavities" does. Understanding this terminology is essential in the context of building construction and mechanical inspection, as it relates to ensuring proper air distribution and system efficiency.