Explanation

The correct answer is C - The team realized that some stories were underestimated relative to other stories and reestimated as needed.
According to the data in the chart:
* Backlog started at 500 points.
* Points steadily decreased by 25 points per iteration for the first 3 iterations, reflecting normal velocity.
* At the end of iteration 4, the backlog increased from 425 to 450 points (a 25-point jump), which indicates an increase in estimated remaining work.
In Agile, backlog point totals can increase when work is reestimated-typically because items were originally underestimated or new complexity is discovered. Reestimation reflects the evolving understanding of requirements and is a core principle of adaptive planning.
From the PMI Agile Practice Guide:
"Estimates may change as the team learns more. Agile teams inspect and adapt their understanding of the work during iteration planning and refinement. Story reestimation is normal and may result in backlog point increases." (PMI Agile Practice Guide, Section 5.3 - Adaptive Planning and Estimation) Mike Griffiths writes:
"Backlogs are dynamic. Teams may reestimate stories during grooming or retrospectives if they find that original estimates were off. This helps maintain planning accuracy and backlog integrity." (Mike Griffiths, PMI-ACP Exam Prep, Chapter 5 - Estimation and Backlog Refinement) Incorrect options:
* A refers to external factors not reflected in the backlog points.
* B would be better handled by new backlog items, not inflating prior estimates.
* D suggests increased scope/output, which would add stories but not necessarily reestimate existing ones.
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When the team is not confident that the solution will work, delivering the minimum marketable feature (MMF) to customers for feedback is the best approach. The MMF represents the smallest, functional version of the product that can provide value to customers. By delivering this early and obtaining feedback, the team can validate assumptions, identify potential issues, and make necessary adjustments before committing to further development. This approach allows for early course correction and ensures the solution aligns with customer expectations and business needs.