A. The Product Owner takes the time between the Sprints to do it.

B. Business Analysts in the organization should do this work for the Scrum Team 1-
2 Sprints ahead of the development Sprints.

C. The Product Owner and the Developers can refine the Product Backlog during any Sprint as needed, ideally in advance of the upcoming Sprint.

D. The Product Owner must do this as essential work in Sprint 0.

E. The Product Owner and the Developers do it in the current Sprint if they have been unable to do it in preceding Sprints.