Effort estimation is a technical task owned by the Developers, who execute the work. The Scrum

Guide notes: "The Developers are responsible for... planning how to deliver the Increment." During

Sprint Planning and refinement, they estimate effort based on their expertise.

A: Correct—the Developers collectively assess what’s needed to meet the Definition of "Done."

B: PMO isn’t a Scrum role; estimation stays within the team.

C: The Product Owner focuses on value and ordering, not technical estimates.

Exact Extract from Scrum Guide: "The Developers are the people in the Scrum Team that are

committed to creating any aspect of a usable Increment each Sprint... They are self-managing,

meaning they internally decide who does what, when, and how." (Section: "The Developers") This

includes effort estimation.

Thus, A is correct.

Reference: Scrum Guide (2020), Section: "The Developers."