Domestic mail is transmitted primarily between which of the following?

The correct answer highlights that domestic mail is transmitted primarily between states and territories, which encompass the entire geographic area within a country's borders. This includes all sending and receiving points within that nation, enabling a structured postal system that facilitates communication and delivery of goods and services across different regions.

In the context of domestic mail, it specifically refers to mail that does not cross international boundaries. This means that options referring to international locations, cities only, or countries do not accurately represent the nature of domestic mail, as they do not encompass the broader scope of connections facilitated by the postal service within a nation. Therefore, focusing on states and territories provides a more comprehensive understanding of domestic mail transmission, illustrating the inner workings of a country's postal system.