单项选择题
Additional heat extraction from the exhaust gases can be effected by adding an （） section to the unit in plants.
A.air cooler B.economizer C.injector D.air blower
单项选择题 Oil water separators are used to ensure that ships don’t discharge oil when （） bilge water.
单项选择题 In general, （） is suitable for delivering small quantifies at high pressure.
单项选择题 Under centrifugal pumps are the volute, diffuser, mixed-flow, axial flow and （） or regenerative types.
