A customer will have ongoing changes to project requirements. Which of the following is the BEST project management methodology for this requirement?

Waterfall is a linear, sequential methodology where requirements are defined upfront and changes are costly and disruptive to incorporate once later phases have begun.

Agile is built around the principle of welcoming changing requirements, even late in development, using short iterative cycles (sprints) that allow teams to reprioritize and adapt continuously. Its core mechanisms - frequent backlog refinement, sprint planning, and stakeholder feedback loops - make it the best fit when a customer expects ongoing changes throughout the project.

PRINCE2 is a structured, stage-based methodology with formal governance and change control processes; it is not optimized for frequent, ongoing requirement changes.

Bottom-up is a cost or effort estimating technique used during project planning, not a project management methodology.