单项选择题
When air is at its dew point it is at its（）
A.lowest absolute humidity B.lowest relative humidity C.highest absolute humidity D.highest relative humidity
单项选择题 The latent heat of water vapor in air is dependent upon the （）
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（）
