What is used to communicate from one city to another?

To communicate from one city to another, you need to go outside the metropolitan area, so the answer to this question is WAN, the vast area network. A MAN is fine for within the city limits including the suburbs and maybe a little surrounding rural area, but not further.

The WAN is designed to cope with the distances involved. A business may still have a private network connecting its branches in different parts of the world, as well as various cities within one country. The WAN can compare all of those sections of the business most effectively. Only if the business is confined to the one city district would it use a MAN.