Answer:
B. Register with the group.
Step-by-step explanation:
A person who wants to join an online discussion group would have to first register with the group.
Basically, a user who is not registered with a web or local computer-based platform is considered to be a guest user and as such this user do not have the ability to post comments (messages) in its discussion group. Therefore, to have the exclusive rights and permission to participate in contributing to an online discussion group, a user must be registered with the platform as a bonafide member.
After the registration is complete, the user will have a user account (profile) which comprises of his login credentials i.e username and password.