What are common types of refrigerants used in modern refrigeration systems?

The selection of HFCs, HCFCs, and natural refrigerants reflects the current trends and regulations within the refrigeration industry. Hydrofluorocarbons (HFCs) are widely used due to their efficiency and minimized impact on the ozone layer compared to older refrigerants like CFCs. Hydrochlorofluorocarbons (HCFCs) serve as transitional options, as they are being phased out under international agreements like the Montreal Protocol.

Furthermore, there is a growing emphasis on natural refrigerants—such as ammonia, carbon dioxide, and hydrocarbons—which are increasingly being recognized for their environmental benefits, including negligible ozone depletion potential and lower global warming potential. This shift towards HFCs, HCFCs, and natural refrigerants demonstrates a comprehensive approach to ensuring efficient cooling while adhering to environmental regulations.

The other options lack accuracy, as they either focus too narrowly, like mentioning only Freon or CFCs and HFCs, or suggest materials that are not relevant to refrigerants, like metals. Thus, the correct choice captures the diversity and evolution of refrigerant usage in modern systems.