Which of the following best describes a necessary characteristic of a good requirement?

A necessary characteristic of a good requirement is that it should be specific and actionable, which often involves considerations of feasibility, including affordability. A good requirement needs to be realistic in terms of the budget and resources available to the project; therefore, ensuring that a requirement is affordable aligns closely with the principles of systems engineering and project management. This is essential because if a requirement is not affordable, it can jeopardize the project's success and lead to scope creep or resource constraints.

In contrast, it's important to avoid options that suggest requirements are based on opinion or vagueness, which can lead to misinterpretation and lack of clarity. Requirements should be precise and measurable to facilitate clear understanding among stakeholders and ensure successful implementation. Also, framing a requirement as optional deviates from the fundamental understanding that requirements define essential features or capabilities that are integral to the system's purpose and functionality. Therefore, the emphasis on affordability underscores the need for requirements to be both achievable and aligned with the project's constraints.