Which of the following is an example of a common refrigerant?

R-134a is known as a common refrigerant, particularly in residential and automotive air conditioning systems. It is a hydrofluorocarbon (HFC) that was widely used because it does not deplete the ozone layer, making it an environmentally preferable option compared to older refrigerants like R-12, which is a chlorofluorocarbon (CFC).

R-134a has effective thermodynamic properties which allow it to efficiently transfer heat, making it suitable for refrigeration systems. In commercial and household appliances, R-134a has been favored due to its lower global warming potential compared to previous refrigerants. It also has a lower boiling point, which is advantageous for cooling applications.

While ammonia is another common refrigerant used in industrial settings because of its high efficiency and low cost, its toxicity and flammability limit its use in smaller systems. Water is also technically a refrigerant and is used in certain applications but is less common in conventional refrigeration systems due to its lower heat transfer capabilities.