Which type of cabin air compressor uses airflow to compress air?

The choice that states both types of compressors, centrifugal and positive-displacement, are capable of using airflow to compress air is accurate.

Centrifugal compressors operate by increasing the velocity of incoming air with a rotating impeller, which through a diffuser converts this velocity into pressure. The airflow is fundamental to their operation since they rely on the motion and kinetic energy of the moving air to achieve compression.

Positive-displacement compressors, on the other hand, work by trapping a specific volume of air and then reducing that volume to create pressure. This also involves airflow, as air flows into the compression chamber, where it is subsequently compressed when the volume is reduced.

Thus, both types utilize airflow in their processes of compressing air, making the selected choice correct. Each method has its specific applications and benefits, which contribute to different operational efficiencies in various aircraft systems.