A centrifugal pump gradually develops insufficient discharge pressure. What corrective action is required?

Correct Answer: Option C — Replace the wearing rings.

Internal recirculation occurs when wearing rings clearances increase due to erosion or cavitation, bypassing fluid from the discharge back to the suction. Replacing these rings restores the design tolerances necessary to maintain the pump's rated discharge pressure and volumetric efficiency, as required by standard centrifugal pump maintenance protocols.