What type of organization does the letter AC represent in web addresses?

The answer to this is letter B or academic. This means that the web address is pertaining to an organization that is an academic establishment or has something to do with education. If you would notice, there are different websites that may have this that are connected to colleges, schools, learning centers, and the like.

This can make it easier for people to distinguish if they are about to check the right website as there are moments when websites seem to be almost the same in terms of addresses. It will be a waste of time to check out a web address that is not what you need.