单项选择题
A.at the compressor discharge
B.at the compressor suction
C.in the expansion valve
D.in the receiver
单项选择题 Which of the listed pressure control valves would be used to establish the maximum operating pressure of a hydraulic system?（）
单项选择题 If a centrifugal bilge pump were continually operated with the discharge valve closed the （）.
单项选择题 In order to accurately measure very low pressures, which of the instruments listed should be used?（）