The main benefit of using a mechanical piston or load-distributing band device for chest compressions is:

A. the minimal training required to correctly operate the devices.
B. the elimination of rescuer fatigue that results from manual compressions.
C. the elimination of the need to place a firm, flat device under the patient.
D. its ability to be used with any patient, regardless of age, weight, or body size.

Answer: B. the elimination of rescuer fatigue that results from manual compressions.