The correct answer is A retention policy, which is a set of guidelines that determine how long certain types of data or documents should be kept before they are destroyed or archived. This is important for compliance with legal requirements and for maintaining a record of incident response activities. Choice B, Destruction Policy, generally refers to the guidelines for secure disposal of data rather than duration it should be retained. Classification Policy (Choice C) describes how information is categorized in terms of sensitivity, not how long it should be kept. Archival Strategy (Choice D) is a broader concept that may involve the utilization of retention policies, but it primarily focuses on the long-term preservation and storage of data rather than the specific duration before disposal.