The correct answer is A. A Cleanup Rule should be placed at the bottom of the rulebase or Ordered Layer. Its function is to handle traffic that has not matched any previous explicit rule. In a secure firewall policy, that normally means dropping or rejecting unmatched traffic and logging it where operationally useful. Option B is wrong because an explicit cleanup rule is a recognized best practice even though the system has implicit cleanup behavior. Option C is incorrect because cleanup rules are not a VPN tunnel termination mechanism. Option D is dangerously wrong: placing cleanup at the top would match broad unmatched traffic before legitimate allow rules, breaking policy and possibly blocking all traffic. The correct rulebase design is specific rules first, broader rules later, and cleanup last. This makes policy behavior predictable, auditable, and aligned with positive-control security design. Reference topics: Cleanup Rule, Access Control rulebase best practices, Ordered Layers, explicit default rule.