单选题A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.Athe four-way control valve failing to shiftBthe bleeder valve sticking in the open positionCcold hydraulic fluidDa clogged air vent falter on the oil reservoir
单选题
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
A
the four-way control valve failing to shift
B
the bleeder valve sticking in the open position
C
cold hydraulic fluid
D
a clogged air vent falter on the oil reservoir
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