Final answer:
The correct definition of a User Requirement is a goal or task that classes of users must be able to achieve with a system, or a desired product feature. User requirements are part of the criteria for designing a system and distinguish from non-functional requirements, system requirements involving subsystems, and broader system properties and constraints.
Step-by-step explanation:
The correct definition of the term User Requirement is A: A goal or task that specific classes of users must be able to perform with a system, or a desired product attribute. User requirements are essentially goals or tasks that the end-users of the system need to be able to accomplish. These requirements translate into features or functions of the system that enable users to perform their tasks effectively. The identification of user requirements is a crucial part of the design and development process, informing decisions about system functionality and design to ensure it meets the needs of its users.
User requirements must be distinguished from other types of requirements such as nonfunctional requirements (option B), which describe how the system performs rather than what it does, and from higher-level systems requirements (option C), which involve multiple subsystems and may encompass both software and hardware. Finally, user requirements are also different from general system properties and constraints (option D), which are broader and may not relate to specific user tasks.
In the context of criteria and constraints, user requirements can be seen as part of the criteria that a successful design must meet to be considered effective. Criteria are measurable standards or attributes of a design, while constraints are conditions or limitations that the design must satisfy. Both are employed to ensure that the design process results in a system that not only functions as intended but also adheres to predetermined limitations, such as cost, time, and material specifications.