Which type of requirement might describe performance metrics for a system?

The correct choice describes non-functional requirements, which are integral to defining how a system performs, rather than what it does. Non-functional requirements encompass various quality attributes, including performance metrics, reliability, security, and usability. Specifically, when it comes to performance metrics, these requirements could specify how fast a system should respond, how many transactions it can handle at once, or how well it performs under various conditions.

Identifying performance as a non-functional requirement helps stakeholders understand overall system behavior and expectations, which go beyond the simple functionality of the system. Consequently, incorporating these into the requirements documentation guides design and implementation to ensure that the system meets necessary performance standards.