The correct answer is C. Freon.
Freon is a generic term for a group of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) that were once widely used as refrigerants. However, these chemicals were found to be harmful to the ozone layer, and their use has been phased out.
Sulphur dioxide is a toxic gas that is not used for refrigeration. Chlorine is a greenish-yellow gas that is used as a disinfectant and bleaching agent. Phosphine is a colorless gas that is used as a pesticide.
Freons are non-toxic and non-flammable, and they have a high boiling point. This makes them ideal for use in refrigeration systems, where they are used to absorb heat from the inside of a refrigerator and then release it to the outside.
Freons are also relatively inexpensive and easy to work with. However, they have been found to be harmful to the ozone layer, and their use has been phased out.
Newer refrigerants, such as hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), are now used in most refrigeration systems. These chemicals are less harmful to the ozone layer than Freons, but they are still greenhouse gases.
The search for a truly environmentally friendly refrigerant is ongoing.