What should the Product Owner do when the Developers are ready to start the first Sprint, but the Product Backlog is not ready yet?

What should the Product Owner do when the Developers are ready to start the first Sprint, but the Product Backlog is not ready yet?
A . The Product Owner should ask the Scrum Master to remove this impediment.
B. The Product Owner should let the team start the Sprint and continue refining the Product Backlog.
C. The Product Owner should not allow the team to Start the Sprint.

Answer: B

Explanation:

Having unready (unrefined) items is not an impediment or even a reason to don’t start a sprint. It is totally okay to refine items during the sprint ("on the fly").