The correct option is Psychological acceptability of controls.

The Psychological acceptability of controls principle emphasizes designing security so that staff find protections easy to use and acceptable. When controls are usable and fit normal workflows people are less likely to create insecure workarounds and compliance with policy improves.

Defense in depth refers to deploying multiple layers of security controls to reduce the chance of a single point of failure. It focuses on redundancy and breadth of protection rather than on making controls easy and acceptable for users.

Economy of mechanism principle stresses simplicity of design to minimize flaws and errors. Simplicity helps security but the principle is about reducing complexity in the implementation rather than directly addressing user acceptance.

Complete mediation principle requires that every access to every resource be checked for authorization. This principle is about enforcement and correctness of access controls rather than about usability or making protections acceptable to people.

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