The correct answer is 'Implementing role-based access control (RBAC) to define user permissions.' This action aligns with the least privilege principle by ensuring users are granted only those permissions necessary to perform their duties, reducing the risk of unauthorized access or escalation of privileges. Conversely, 'Providing all staff with equivalent comprehensive privileges to streamline operations' is incorrect as it excessively broadens access, increasing the attack surface. 'Consolidating high-level privileges into a shared management account for convenience' incorrectly increases the risk of privilege misuse or elevation if the account is compromised. 'Enabling personnel to self-grant permissions when faced with access restrictions' is also incorrect as it may lead to permissions being granted without proper authorization, violating the principle of least privilege.