The correct answer is A - Stakeholders should have regularly been engaged to obtain feedback and reduce the functionality risk.
In Agile, stakeholder engagement and iterative feedback loops ensure that the solution being built is aligned with business value. Simply meeting documented requirements is insufficient. Agile practices such as demos and user feedback sessions minimize the risk of building features that fail to deliver value.
PMI Agile Practice Guide:
"Agile emphasizes ongoing stakeholder engagement. Demonstrating working software at the end of each iteration and gathering feedback ensures that the product is delivering business value." (PMI Agile Practice Guide, Section 4.2 - Stakeholder Engagement) Mike Griffiths states:
"Value-driven delivery is achieved not just by delivering what was asked for, but by ensuring it actually meets customer needs. Regular feedback from stakeholders is critical to avoid building low-value features." (PMI-ACP Exam Prep, Chapter 3 - Value-Driven Delivery) Incorrect options:
* B refers to the lean principle of "decide as late as possible," but feedback, not delay, would have addressed the issue.
* C is unrelated to this context.
* D lacks the collaborative engagement approach emphasized in Agile.