The best way to respond to Peter's concerns about the Scrum Team's productivity and progress is by sharing the Product Backlog, the projections towards the release dates, and ensuring that Peter has access. This approach provides transparency, which is a fundamental principle of Scrum. It allows Peter to see the work that has been planned, the progress being made, and how it aligns with the release objectives. This information helps manage expectations and facilitates better communication and collaboration between the team and stakeholders.