单选题Shaft sealing in a centrifugal pump can be effected by （）.Athe mechanical sealBpacked stuffing boxesCeither A or BDneither A nor B
单选题
Shaft sealing in a centrifugal pump can be effected by （）.
A
the mechanical seal
B
packed stuffing boxes
C
either A or B
D
neither A nor B
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