A space on a server where users can interact with one another as if in a physical room is called a a. blog. b. mailing list. c. chat room. d. newsgroup.

 c. chat room.

In the context of online communications, here's what each of the terms means:

a. Blog: A blog (short for "weblog") is a website or part of a website that contains regularly updated content, typically written in an informal or conversational style. Blogs can be personal or professional, and they often focus on a particular subject or theme. Readers may have the chance to comment on blog posts, but the interaction is not in real-time.

b. Mailing List: A mailing list is a group of email addresses used to distribute content to multiple recipients. When you send an email to the mailing list address, everyone who is subscribed to the list receives the email. It's a way to reach a group of people who are interested in a specific topic, although not necessarily interactive in real-time.

c. Chat Room: A chat room is an online space where users can communicate with each other in real-time. Messages are typically short and appear quickly after they are sent, which allows for a flowing conversation among participants, much like talking. Chat rooms can be public or private and are used for a variety of purposes, from social to business-related discussions.

d. Newsgroup: A newsgroup is a part of the Usenet system which preceded the World Wide Web. It's similar to a forum where users can post messages about different topics, and others can then read and respond to these messages. Newsgroups are categorized and can cover a vast array of subjects, but interactions don't happen in real-time like in chat rooms.