Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by __________.

Correct Answer: Option D — cavitation

Cavitation occurs when local pressure drops below the fluid's vapor pressure, causing vapor bubbles to form. When these bubbles collapse against the impeller surface, they create high-energy shock waves that erode the metal, resulting in the characteristic pitting found in the suction areas of centrifugal pump impellers.