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

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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

单项选择题

If a centrifugal pump is driven by a constant speed electric motor and produces a discharge pressure less than designed, the cause is probably（）.

A.excessive pump speed
B.excessive suction head
C.worn wearing rings
D.gross pump misalignment

单项选择题

Which of the following statements is correct relative to distillation plant operation?（）

A.Distillation is the process of boiling seawater to produce vapor which is condensed into fresh water
B.Evaporation is the second part of the distillation process where brine is removed
C.Brine is the result of condensed sea water vapor
D.Distillate is the product resulting from the evaporation of fresh water vapor