According to the CISSP Official (ISC)2 Practice Tests3, the most suitable approach that the administrator should take when a user requests read-only access to files that are not considered sensitive in a Discretionary Access Control (DAC) methodology is to request data owner approval to the user access. DAC is a type of access control that grants or denies access to an object based on the identity and permissions of the subject, and the discretion of the owner of the object. The owner of the object has the authority and responsibility to determine who can access the object and what level of access they can have, such as read, write, execute, or delete. The owner can also delegate the access rights to other subjects or groups, or revoke them as needed.
The administrator is the person who manages and maintains the system and the access control mechanisms, but does not have the authority to grant or deny access to the objects without the owner's consent. Therefore, the administrator should request data owner approval to the user access, regardless of the sensitivity of the files, to ensure that the access is authorized and compliant with the DAC methodology. Requesting manager approval for the user access is not the most suitable approach, as the manager may not be the owner of the files, and may not have the authority or knowledge to grant or deny access to the files. Directly granting the access to the non-sensitive files is not the most suitable approach, as it may violate the DAC methodology and the owner's discretion, and may introduce unauthorized or excessive access to the files. Assessing the user access need and either granting or denying the access is not the most suitable approach, as it may violate the DAC methodology and the owner's discretion, and may introduce unauthorized or excessive access to the files. References: 3