单项选择题
A.gravity and feed oil cups B.grease cups C.hand during installation D.leakage through the stuffing box
The steam coils in a high pressure evaporator used for ...
单项选择题The steam coils in a high pressure evaporator used for saltwater service should be de-scaled with （）.
A.a needle gun B.soap and water C.a wire brush D.a chipping hammer
Which of the listed chemicals can be routinely used to ...
单项选择题Which of the listed chemicals can be routinely used to maintain the hygienic quality of potable water?（）
A.Hydrochloric acid B.Chlorine C.Sulfuric acid D.Zinc chromate
The ratio of the weight of moisture contained in a give...
单项选择题The ratio of the weight of moisture contained in a given volume of air, to the weight of moisture that the same sample would hold if saturated, is called the（）.
A.absolute humidity B.relative humidity C.specific humidity D.total humidity
