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What causes cavitation in a centrifugal pump ________．
A.Vapor pockets in the flow stream
B.Rough impeller surfaces
C.Worn wearing rings
D.Heavy fluid in the flow stream
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单选题Which of the listed conditions can lead to cavitation气穴in a centrifugal pump?（）A
Vapor pockets formed in the suction flow streamB
Rough easing volute surfacesC
Worn wearing ringsD
Heavy fluid in the flow stream
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