单项选择题
A.the same, whether at sea, or during maneuvering
B.adjusted during each hour of operation while at constant RPM
C.higher at sea than while maneuvering
D.lower at sea than while maneuvering
单项选择题 The crankcases of many diesel engines are kept under a slight vacuum to （）
单项选择题 Which of the following conditions could cause the feed pump for an auxiliary boiler to lose suction?（）
单项选择题 In readying an auxiliary water-tube boiler for a routine hydrostatic test, which of the following procedures should be undertaken prior to filling the boiler with fresh water?（）