In an agile or adaptive environment, as outlined in the Agile Practice Guide and the PMBOK® Guide, quality is not a phase or a separate department ' s responsibility; it is " built-in " to the process.

Collective Responsibility: Unlike traditional (predictive) projects where a separate Quality Assurance (QA) team might perform inspections at the end of a phase, Agile teams follow the principle of collective ownership. Every team member—developers, testers, and even the Product Owner—is responsible for the quality of the increments being produced.

Continuous Quality: Quality control activities occur " throughout the project life cycle " rather than at specific intervals. This is achieved through practices such as:

Pair Programming: Real-time code review and quality checking.

Test-Driven Development (TDD): Writing tests before the code itself to ensure requirements are met.

Continuous Integration (CI): Frequently integrating work to catch defects early.

Definition of Done (DoD): A shared checklist that every work item must meet to ensure consistent quality before it is considered complete.

The Role of the Team: Agile teams are cross-functional. This means the people doing the work are also the ones verifying it, leading to faster feedback loops and a significant reduction in rework.

Analysis of Other Options:

A. A group of quality experts at specific times during the project: This describes a traditional " Silo " or Waterfall approach where quality is a hand-off. In Agile, waiting for " specific times " or external experts creates bottlenecks.

B. The project manager only: In Agile, the Project Manager (or Scrum Master) acts as a servant-leader who facilitates the process. They do not have the technical oversight to perform all quality control activities personally.

D. Selected stakeholders at specific times during the project: While stakeholders participate in the Sprint Review to validate that the product meets their needs, the actual quality control (ensuring the product is built correctly and is free of defects) is the responsibility of the delivery team during the iteration.