Vacuum efficiency is measured by combining which two factors?

Vacuum efficiency is primarily determined by assessing airflow and lift. Airflow, measured in inches of mercury (Hg) or water (H2O), indicates the volume of air that the vacuum can move, while lift refers to the vacuum's ability to pick up debris from the surface. When these two factors work together, they provide a complete picture of how effectively the vacuum can clean a surface.

The combination of high airflow and sufficient lift means that the vacuum can not only draw in air and dirt but also effectively separate the dirt from the carpet fibers. Lifting dirt from the surface is crucial for deep cleaning. Thus, understanding and optimizing both factors is essential for evaluating the performance capabilities of a vacuum cleaner in professional carpet cleaning.

Other options incorporate elements such as noise level and power consumption, which, while relevant to the operation of a vacuum, do not directly measure its cleaning capability in the same way that airflow and lift do. This focus on airflow and lift underlines why choice C correctly represents the factors that determine vacuum efficiency.