Which policy defines a set of rules for storing and maintaining data for operational and regulatory purposes?

The correct choice is a data retention policy. This policy outlines the guidelines and procedures for how an organization manages its data, including how long data should be stored, when it can be deleted, and the requirements for maintaining data for compliance with legal and regulatory standards. A well-defined data retention policy helps ensure that necessary data is preserved for operational needs while also addressing any legal obligations related to data storage.

The other options relate to different aspects of data management and security. An access control policy focuses on regulating who can access certain data and the conditions under which they can access it. An incident response policy deals with the procedures to follow when a security breach occurs, ensuring that the organization can respond effectively to mitigate any impact of the incident. A data encryption policy specifies how sensitive data should be encrypted to protect it from unauthorized access, but it does not pertain to the retention or maintenance of that data over time.