单选题Pressure in an operating hydraulic system is developed （）.Aonly by the pump as its primary functionBby resistance to the fluid flow through the systemCby the thermal input to the systems fluidDsolely by the charge applied by the accumulators
单选题
Pressure in an operating hydraulic system is developed （）.
A
only by the pump as its primary function
B
by resistance to the fluid flow through the system
C
by the thermal input to the systems fluid
D
solely by the charge applied by the accumulators
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