单项选择题
In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decomposes and from （）.
A.petroleum crystals B.phosgene gas C.water vapor D.carbon monoxide
单项选择题 In an operating refrigeration system low on refrigerant, a liquid line sight glass will（）
单项选择题 The thermal expansion valve reacts directly to the （）
单项选择题 One function of the thermal expansion valve is to（）
