Which of the following best describes non-functional requirements?

Non-functional requirements are essential aspects of system development that focus on the qualities and characteristics of how a system operates, rather than what it does. The correct choice accurately emphasizes this distinction by highlighting requirements that define how a system performs under certain conditions. These requirements encompass attributes such as performance, security, usability, reliability, and scalability, which are crucial for ensuring that the system not only fulfills its intended functions but also meets the necessary performance standards in various operational scenarios.

While the other choices touch on components of system development, they do not accurately represent non-functional requirements. For example, the first choice refers specifically to functional requirements, which describe what a system should achieve rather than how well it should perform. The third option focuses on documentation processes, which is more about how requirements are captured and recorded than the performance characteristics of the system itself. The fourth choice relates to stakeholder management, which deals with engaging and communicating with stakeholders rather than defining the parameters of system performance. Thus, the focus on performance under specific conditions makes the chosen answer the most appropriate descriptor for non-functional requirements.