单项选择题
In order to accurately measure very low pressures, which of the instruments listed should be used?（）
A.Compound gage
B.Bonrdon tube
C.Manometer
D.Deadweight gage
单项选择题 Reduced capacity, accompanied by vibration and noise at the suction of a centrifugal pump is a result of （）.
单项选择题 The refrigerant leaves the evaporator of a refrigeration system as a low pressure （）.
单项选择题 When operating with a negative suction head, which of the following types of pumps will require priming?（）