If a team completes the work in their iteration backlog earlier than expected, the best course of action is to work with the product owner to pull more work from the product backlog into their iteration backlog. This approach keeps the team productive and focused on delivering value, rather than waiting or working on non- critical tasks. Option A suggests working on non-critical tasks, which does not maximize value delivery.
Option B (waiting for other groups) is not a productive use of time. Option D (reporting differences in completion time) is helpful for future planning but does not address the immediate need to keep the team engaged.