The forum formed for the discussion on a particular subject through the use of the Internet is known as:

The correct answer is B. Newsgroup.

A newsgroup is an online discussion forum where participants can post messages and engage in conversations about specific topics. Unlike chat rooms or social media, newsgroups often rely on a series of messages organized by subject, which allows members of the group to communicate asynchronously. If you need further assistance or have more questions, feel free to ask!