The correct answer is Mandatory access control (MAC), as it enforces security policies that are centrally controlled by a security policy administrator. Users do not have the ability to override the policy or share resources unless the policy permits them to do so, making it suitable for environments with stringent security requirements. All access attempts are compared against the policy, which maintains a high level of security. Attribute-Based Access Control (ABAC) allows policies to use multiple attributes (user, resource, environment) to make access decisions, which can be more flexible but less strict than MAC. Role-Based Access Control (RBAC) is not necessarily tied to data classification or clearance levels. Access Control Lists (ACLs) are used to specify which users or system processes are granted access to objects; they don't inherently provide the systematic, policy-driven approach required in the scenario.