Hydraulic machinery failures are commonly caused by contamination of the hydraulic fluid and （）.

A.refrigerant must be bled off the sensing line before adjustments are made
B.all refrigerant must be pumped into the receiver before adjustments are made
C.time must be allowed for conditions to stabilize in the evaporator before further adjustments are made
D.all refrigerant must be routed through the dehydrator while changing the superheat setting

A.motor controller overload would open
B.pump would eventually overheat
C.relief valve would continuously cycle open
D.motor would overheat

A.have a greater head capacity
B.operate with increased impeller efficiency
C.discharge through the suction side of the pump casing
D.require more power to run the shaft