The AHRI definition of standard air is:

The correct answer is based on the standard conditions defined by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) for standard air. According to the AHRI, standard air is specifically defined as air weighing 0.075 lb/ft³ at a temperature of 70°F and a barometric pressure of 29.92 inches of mercury (in Hg).

This definition provides a consistent reference point for calculations in heating, ventilation, and air conditioning (HVAC) applications. Standardizing the properties of air is crucial for estimating the performance of HVAC systems, as temperature and pressure can significantly influence air density.

Other choices present different conditions or weights for air, but they do not align with the AHRI definition. For instance, while one option mentions standard air at sea level, it does not specify the temperature that must accompany it. Additionally, another option cites a weight of air that does not reflect the temperature and pressure specified by AHRI. Only the correct choice connects the weight, temperature, and exact barometric pressure, thus fulfilling the definition set forth by AHRI for standard air in HVAC calculations.