____________ is used in mission critical systems and applications to lock down information based on sensitivity levels (Confidential, Top Secret, etc..

Mandatory Access Control (MAC) is an access control model where the operating system or security kernel enforces access rules based on security labels assigned to subjects (users/processes) and objects (files/resources). In MAC, the administrator, not the owner, defines these labels and policies (e.g., Top Secret, Confidential), making it ideal for high-security, mission-critical systems requiring strict information lockdown.

Discretionary Access Control (DAC) allows resource owners to grant or deny access to their resources, which is less restrictive and unsuitable for mission-critical systems requiring centralized, non-discretionary enforcement of sensitivity levels.

Strategic Access Control (SAC) is not a recognized standard access control model in information security.

Limited Access Control (LAC) is not a recognized standard access control model in information security.