When user stories are not fully completed during an iteration, it often indicates that the team's velocity or sprint planning is unrealistic. The Scrum Master should facilitate a discussion to revalidate and adjust the team's velocity and ensure that user stories are sized and selected to allow for both development and testing within the same iteration.

The Agile Practice Guide emphasizes maintaining a sustainable pace and complete definition of done.

Option A is anti-agile (splitting user stories by function defeats cross-functional work).

Option B adds resources without addressing root cause.

Option D undermines sustainable delivery and Agile principles.