When a requirement appears between the product requirement document and the detailed design document, what has likely happened?

When a requirement appears between the product requirement document and the detailed design document, it typically indicates that the development team has added that requirement during the design phase. This situation can arise because the development team, upon analyzing the product requirements in detail, may identify additional aspects or functionalities that are necessary to implement the aforementioned requirements effectively.

The design process often reveals more about the system's architecture and technology constraints, leading developers to suggest enhancements or alterations that may not have been initially captured in the product requirements. This is a natural part of Software Development Life Cycle (SDLC) and reflects a collaborative effort to ensure that the final product meets both functional and non-functional requirements.

In this context, the other options are less likely to be true. While business analysts, test teams, or customers can contribute to the requirements gathering process, the actual addition of requirements during the transition to detailed design is generally the responsibility of the development team, tasked with translating high-level requirements into actionable design elements.