The best answer is C. When multiple Scrum Teams are working together on a product, they must mutually define and comply with the same Definition Of Done.
According to the Scrum Guide1, “the Definition of Done is a formal description of the state of the Increment when it meets the quality measures required for the product.” The Scrum Guide also states that “when multiple Scrum Teams are working together on a product, they must mutually define and comply with the same Definition of Done. This ensures transparency and consistency among the teams and makes their combined work potentially releasable.”
A, B, and D are not correct answers.
A. Each Scrum Team uses its own, but must make their definition clear to all other teams so the differences are known.
This answer does not reflect the Scrum value of alignment2. Having different Definitions of Done for each Scrum Team can create confusion and inconsistency in the quality and completeness of the product. It can also make it difficult to integrate and deliver a coherent and valuable Increment at the end of each Sprint.
B. The Scrum Masters from each Scrum Team define a common Definition of Done.
This answer does not reflect the Scrum principle of self-organization3. The Definition of Done should be created by the Developers who are responsible for delivering the Increment, not by the Scrum Masters who are responsible for facilitating and coaching the Scrum Teams. The Scrum Masters can help the Developers understand and apply the Definition of Done, but they should not impose it on them.
D. Each Scrum Team defines and uses its own. The differences are discussed and reconciled during a hardening Sprint.
This answer does not reflect the Scrum value of focus2. Having different Definitions of Done for each Scrum Team can lead to technical debt or rework that requires a hardening Sprint to resolve. A hardening Sprint is an anti-pattern that violates the rule of delivering a potentially releasable Increment at the end of each Sprint4.