A Product Owner wants advice from the Scrum Master about estimating work in Scrum. Which of these is the guideline that a Scrum Master should give? (Choose the best Answer)

A fundamental principle in Scrum is that the people who will perform the work are in the best position to estimate the effort involved. Therefore, the Developers are responsible for sizing or estimating Product Backlog Items. They have the most insight into the technical complexity and effort required to turn a Product Backlog Item into a "Done" Increment. The Scrum Master should coach the Product Owner and the team on this principle, ensuring that estimates are generated by the Developers to foster accuracy, commitment, and self-management.

A. Story points are a popular technique for estimation, but Scrum does not prescribe any specific unit; teams can choose what works best.
C. Relative units are a common and recommended practice in agile estimation, but they are not a mandatory rule in the Scrum framework.
D. Scrum does not forbid estimating. Sizing Product Backlog items is a crucial activity for planning and forecasting.
E. The Product Owner is accountable for product value, not for estimating the effort of the work. This is the Developers' responsibility.

1. Schwaber, K., & Sutherland, J. (2020). The 2020 Scrum Guide. Scrum.org. p. 7. "The Developers who will be doing the work are responsible for the sizing."

2. Verheyen, G. (2013). Scrum: A Pocket Guide. Van Haren Publishing. p. 68. "The Development Team is responsible for all estimates."