单项选择题
To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air conditioning system, you should （）
A.admit only enough fresh outside air to provide proper ventilation B.reduce the air reheating system load C.lower the compressor head pressure D.operate the purge recovery unit continuously
单项选择题 When air is at its dew point it is at its（）
单项选择题 If you find an extremely large refrigerant leak while using a halide torch, your flame will（）
单项选择题 Before charging a refrigeration unit, the refrigerant charging lines should be（）
