The methodology described is Agile. Key characteristics mentioned in the scenario, such as welcoming changing requirements and conducting daily 'scrum' meetings, are fundamental principles of the Agile approach. Agile is an iterative project management philosophy that prioritizes flexibility, customer collaboration, and rapid delivery in response to change. Scrum is one of the most popular frameworks used to implement Agile, and the daily scrum is a core ceremony within this framework for team synchronization and progress tracking. This approach is particularly effective for complex projects like software development where requirements are expected to evolve.

A. project diamond: This is a model for classifying projects based on their characteristics (novelty, technology, complexity, pace), not a methodology for executing them.

B. waterfall: This is a linear, sequential methodology where requirements are fixed at the start, and changes are difficult and discouraged, which is the opposite of the scenario.

D. Lean: While Lean principles can be complementary to Agile, its primary focus is on eliminating waste. The specific term 'scrum' is a hallmark of the Agile framework.

1. Schwaber, K., & Sutherland, J. (2020). The Scrum Guide. Scrum.org. This official guide defines the Scrum framework, which is a subset of Agile. It explicitly details the "Daily Scrum" (p. 9) as a 15-minute event for the Developers of the Scrum Team to inspect progress and adapt the plan for the next 24 hours.

2. Beck, K., et al. (2001). Manifesto for Agile Software Development. Agile Alliance. This foundational document states a core value as "Responding to change over following a plan," which directly supports the scenario's mention of welcoming changing requirements.

3. Shenhar, A. J., & Dvir, D. (2007). Reinventing project management: The diamond approach to successful growth and innovation. Harvard Business Press. Chapter 2 introduces the Diamond Model as a framework for project classification, distinguishing it from execution methodologies like Agile or Waterfall.

4. Project Management Institute. (2017). A Guide to the Project Management Body of Knowledge (PMBOK® Guide) – Sixth Edition. Section 1.2.4.4 describes the Waterfall method as having "sequential phases" where "the project team proceeds to the next phase only when the previous phase is complete," highlighting its inflexibility to change.