The correct option is An outside collaborator cannot be added to any team in the organization.

Teams are an organization feature that group members for permission management and notifications. Outside collaborators are not organization members, so they cannot be placed on teams and must receive repository access directly. This is the key limitation that fits the scenario of giving time-bound access to a single private repository.

An outside collaborator is not required to enable two factor authentication when the organization enforces it is incorrect. When an organization requires two factor authentication, members and outside collaborators must enable it or they lose access to the organization and its repositories.

An outside collaborator can view every team and the full list of members in the organization is incorrect. Outside collaborators are not members and cannot browse organization teams, and they cannot see the full member roster. At most they can see public information such as members who have chosen to make their membership public.

An outside collaborator can @mention any visible team in issues and pull requests is incorrect. Team visibility is limited to organization members and secret teams are hidden from everyone else. Since outside collaborators are not members they cannot see teams and their mentions will not resolve or notify the team.

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