Which of the following is an example of a functional requirement?

A functional requirement specifies a particular behavior or function of a system. The user authentication process is a clear example of this, as it defines how a user will interact with the system to verify their identity. This includes requirements such as the need for a username and password, the handling of authentication errors, and the processes for logging in and out. These elements directly influence how the system behaves from a user's perspective and fulfill specific business needs.

In contrast, system uptime, response time, and data processing speed focus on non-functional aspects of a system. System uptime refers to the availability of the system, indicating how often it is operational. Response time pertains to the speed at which the system responds to user inputs, while data processing speed indicates how quickly the system can process given data. While these are important for assessing system performance and user experience, they do not specify particular functions or behaviors that the system must exhibit.