单项选择题
More than one stage of evaporation can take place by admitting the sea water into chambers with progressively （） pressure in the flash evaporator.
A.lower B.higher C.the lower D.the higher
单项选择题 In the process of （）, liquid changes into gas.
单项选择题 The designed capacity is 25 tons a day, but the fresh water generator can only （） 22 tons at present.
单项选择题 Clean oil is achieved in a clarifier bowl where the impurities and water collect at the bowl （）.
