单项选择题
Condensate must be drained periodically from the air compressor receivers to prevent （）.
A.second stage cylinder lockup B.oil sump contamination C.faulty operation of pneumatic valves D.corrosion of air receiver baffles
单项选择题 Overheating of a hydraulic system may be a result of （）.
单项选择题 The purpose of the low pressure cut-out switch is to （）.
单项选择题 The process of boiling seawater in order to separate it into freshwater vapor and brine is usually defined as （）.
