单选题When a hydraulic vane pump is working, which of the following is in contact with the vanes?（） (1) the rotor (2) the internal surface of the housing (3) the external surface of the housingA(1) onlyB(2) onlyC(1) and (2)D(1), (2) and (3)
单选题
When a hydraulic vane pump is working, which of the following is in contact with the vanes?（） (1) the rotor (2) the internal surface of the housing (3) the external surface of the housing
A
(1) only
B
(2) only
C
(1) and (2)
D
(1), (2) and (3)
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