Which of the following best describes an incremental development model?

An incremental development model is characterized by its approach to requirements and testing, where both evolve progressively throughout the development process. This model emphasizes the idea of building a system in small, manageable increments or iterations, where each increment adds additional functionality to the existing system.

In this context, establishing requirements and testing progressively allows teams to adapt to changing needs and feedback from stakeholders after each increment. It fosters collaboration and enables developers to focus on the most critical aspects of the software first, assuring that each part is tested properly before moving on to subsequent increments. By this method, the overall risk is reduced, and the product can be adjusted as new insights emerge during development.

The other choices lack this emphasis on progressive enhancement and ongoing testing, which are fundamental to the incremental development model. This continuous evolution and feedback loop are what make option C the best description of this approach.