Final answer:
option d,The absence of moisture is necessary to prevent the formation of acids or blockages and to ensure the efficiency and longevity of the refrigeration system.
Step-by-step explanation:
The question regarding the properties of oil in a refrigerant asks which characteristic it should possess. The correct answer is that the oil should not contain moisture. Oils in refrigeration systems must have certain properties, such as a high boiling point, low volatility, and high viscosity; they should also ignite with difficulty. These properties help maintain the efficiency and safety of the refrigeration cycle and prevent damage to the system. Specifically, the absence of moisture in refrigeration oil is crucial because the presence of water can lead to the formation of acids or other corrosive substances, which can cause system degradation and decreased performance.
Moisture in the refrigeration system can freeze and cause blockages, or react chemically with the refrigerant leading to harmful compounds and system failures. Hence, it's vital for the refrigeration oil to be dry to ensure the longevity and proper functioning of the refrigerant system. Moreover, an oil with a low flash point could pose a fire hazard, while a high pour point could lead to issues with oil flow at low temperatures, and high viscosity oil might not circulate properly. Therefore, the key characteristic to maintain system integrity and performance is that the oil should not contain moisture.