The correct answer is C - Conducted an end-of-phase demonstration.
Agile emphasizes continuous feedback. Regular demonstrations (e.g., sprint reviews or product demos) allow stakeholders, including the customer, to inspect the product increment and provide real-time feedback. Had the team demoed the product, they might have discovered the deficiencies before release.
PMI Agile Practice Guide states:
"A demo or review allows stakeholders to inspect the product increment and provide feedback.
Demonstrations reduce the risk of unmet expectations and confirm that the team is building the right product." (PMI Agile Practice Guide, Section 5.7 - Reviews and Demos) Mike Griffiths writes:
"Agile avoids large, end-of-phase validations. Instead, customer feedback is solicited at the end of every iteration through structured demos. This allows for early course correction and alignment with expectations." (PMI-ACP Exam Prep, Chapter 3 - Value-Driven Delivery) Other options:
* A is a waterfall artifact and not aligned with agile workflows.
* B is analysis-heavy and doesn't ensure real stakeholder feedback.
* D (retrospective) improves process, not product validation.