单项选择题
A.large conical springs
B.compressed air pressure
C.hydraulic pressure
D.exhaust gas pressure
单项选择题 The water in an operating auxiliary boiler should be tested for alkalinity and chloride content each（）.
单项选择题 On a turbo-charged, medium-speed diesel engine, which of the following problems is an indication of a restricted air intake passage?（）
单项选择题 The jacket water temperature in a diesel engine closed freshwater cooling system is normally controlled by （）