单项选择题
In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.
A.saltwater heater shell
B.second-stage condenser
C.atmosphere
D.second-stage flash chamber
单项选择题 Which of the listed characteristics of lube oil are the most important to the engineer from an operational standpoint?（）
单项选择题 Which of the following statements describes the function of an air compressor intake filter?（）
单项选择题 Hydraulic cranes must be properly warmed-up before being operated because （）.