Midway through a Sprint, the Developers tell the Scrum Master they have discovered that one Product Backlog item is far more complex than estimated and that finishing it as originally scoped would jeopardize the Sprint Goal. They want to renegotiate with the Product Owner. What is the most appropriate way for the Scrum Master to serve the Scrum Team here?
The Scrum Master serves the Scrum Team by facilitating events and removing obstacles to progress, and the emerging complexity is exactly such an obstacle. Bringing the Developers and Product Owner together lets the people who own the work and the people who own the value renegotiate scope collaboratively, keeping the Sprint Goal intact. This respects the Developers' authority over the Sprint Backlog.
Why this answer
The Scrum Master serves the Scrum Team by facilitating collaboration and helping remove impediments, and here the impediment is a mismatch between new learning and the original plan. The Developers own the Sprint Backlog and may adapt it, while the Product Owner owns value and scope negotiation. Facilitating that conversation protects the Sprint Goal without overriding either role's authority.
Exam trap
The trap here is treating the Sprint Backlog as a fixed contract that must be delivered exactly as planned, rather than a flexible plan the Developers may adjust as they learn.