Which element is used as refrigerants and as an anticavity dental treatment?

Fluorine is the correct choice because it is a key component in many refrigerants, particularly in the form of hydrofluorocarbons (HFCs), which have largely replaced older refrigerants that are more harmful to the ozone layer. Additionally, fluoride, a compound derived from fluorine, is commonly used in dental treatments to prevent cavities and strengthen tooth enamel. This dual role in both cooling systems and dental care showcases fluorine’s versatility in both industrial and health-related applications, making it an essential element in these fields.

The other elements listed, while they have their own uses, do not share the same connection to both refrigeration and dental care. Chlorine is commonly used for water purification and disinfectants, argon is often employed in inert gas applications like welding or lighting, and oxygen is essential for respiration and combustion but does not serve the roles that fluorine does in refrigeration and dental health.