Comprehensive and Detailed In-Depth Biometrics (such as fingerprint scanning, retinal scanning, or facial recognition) is the most secure method because it authenticates individuals based on unique physical characteristics that cannot be easily duplicated or shared. A . Smart cards - More secure than passwords but can be lost or stolen. B . Key fobs - Provide access control but can be stolen or cloned. D . Security guard - Can enhance security but is prone to human error and does not offer automated access control. Reference: CompTIA A+ 220-1102, Objective 2.2 - Security Best Practices