Explanation
A requirement is considered valid as long as the business stakeholders need it. This is true for ongoing requirements that are reused in the organization.
Answer D is incorrect. This isn't a valid statement as to why satisfied requirements are still considered requirements.
Answer B is incorrect. This isn't a valid statement as to why satisfied requirements are still considered requirements.
Answer A is incorrect. This isn't a valid statement; the ability to change a requirement doesn't make it necessarily a satisfied requirement.

Explanation
Stakeholder Engagement Approach: provides collaboration and communication approaches that might be effective during elicitation.