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

Correct Answer: Option B — Replace the wearing rings.

Gradual loss of discharge pressure in a centrifugal pump typically indicates internal recirculation caused by excessive clearance between the impeller and casing. Replacing the wearing rings restores the design tolerances, effectively minimizing internal leakage and returning the pump to its rated performance capacity as specified in standard marine pump maintenance manuals.