Which type of domain extension is used for sovereign states?

The correct answer is the type of domain extension known as Country Code Domain Extension. These domain extensions are two-letter codes that are specifically assigned to individual countries and sovereign states. For example, ".uk" represents the United Kingdom, ".fr" is for France, and ".jp" is for Japan.

The purpose of these country code domain extensions is to identify websites that are associated with specific geographic locations, allowing for better localization of internet use and content. This also can signal to users that a website has content relevant to a particular country.

In contrast, other types of domain extensions serve different purposes. Specialized domain extensions refer to domains that are designed for specific types of organizations or purposes but are not limited to sovereign states. Unrestricted domain extensions can be registered by anyone, regardless of geographic location or purpose, while restricted domain extensions have specific criteria for registration, often limited to certain entities. Therefore, the unique focus of country code domain extensions on sovereign states makes them the correct answer.