单项选择题
A.fill the unit with saltwater
B.fill the unit with de-scaling compound
C.completely drain the unit
D.tightly seal the unit to exclude air
单项选择题 A distinguishing feature of an educator, when compared to other pumps, is the （）.
单项选择题 The heat required to change a substance from a liquid to a gas without experiencing a temperature change is defined as the latent heat of （）.
单项选择题 Which of the processes listed consumes the greatest amount of power while producing the greatest amount of heat?（）