The key Agile principle is early and continuous delivery of valuable software, coupled with constant customer collaboration and feedback. If deliverables are not meeting customer expectations, the root cause is likely a breakdown in feedback loops. Establishing a continuous feedback environment ensures stakeholder input is captured early and often, allowing teams to course-correct before features are completed and delivered.
According to the Agile Practice Guide: "Customer engagement and continuous feedback loops help ensure that the solution meets business needs and expectations." Option D (retrospective) is important but retrospective happens after the sprint; Option A (continuous feedback) is more proactive and prevents dissatisfaction before it grows.
References:
Agile Manifesto: "Customer collaboration over contract negotiation"
Agile Practice Guide, Chapter 4: "Feedback and Adaptation"
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