What type of requirements specifies how a system should behave under specific conditions?

The correct answer is Non-functional Requirements. Non-functional requirements define the quality attributes, system performance, and operational constraints that a system must meet to ensure satisfactory performance under various conditions. These requirements focus on how the system performs a task rather than the specific behaviors or functions it must execute.

For instance, non-functional requirements might include aspects such as system reliability, response time, scalability, and usability. They establish criteria such as how the system should respond to heavy loads or how secure it needs to be against unauthorized access, thereby ensuring that the system behaves appropriately even when subjected to different operational pressures or conditions.

In contrast, functional requirements lay out what the system should do—specifying the functions and features that must be included. Technical requirements focus more on the technological specifications needed to implement and support the system. Business requirements outline the high-level goals and needs of the organization that are to be satisfied by the project or solution. While all these types of requirements are important, it is the non-functional requirements that address how the system should behave in various situations, which makes this choice the correct answer.