单项选择题 Air conditioning is the process of treating air to control （） its temperature, humidity, cleanliness and distribution to meet the comfort requirements of the occupants of the conditioned space.

单项选择题 （）, iea steam cooler, may be filled in the boiler system to control the superheated steam temperature.

单项选择题 Upon the completion of required tests, a （） should be placed on each extinguisher, showing the date and the person who completed the tests.