Final answer:
The team members and the team's Product Owner are the two groups that must attend every Iteration Review to showcase work and ensure alignment with the product goals.
Step-by-step explanation:
The two groups that should attend every Iteration Review for a given team are b) the team members and c) the team's Product Owner. The team members are involved as they have worked on the tasks during the iteration and need to demonstrate the work they've accomplished. The team's Product Owner must attend to review and accept the completed work, ensuring that it aligns with the product vision and goals. The Scrum Master typically facilitates this event, and while the involvement of the Business Owners or Product Owners from dependent teams may be beneficial for transparency and collaboration, their attendance is not mandatory at every Iteration Review.