File permissions are a fundamental security mechanism in multi-user operating systems. They define access rights (e.g., read, write, execute) for the file's owner, a designated group, and all other users. This system ensures that users can only access and modify files for which they have been granted explicit authorization, thereby protecting data privacy and integrity from unauthorized access by other users or programs.

B. Screen brightness is a user-interface setting for the display hardware and has no connection to file system security or access control.

C. Monitor resolution is a display setting that determines the clarity and size of on-screen elements, not a security feature.

D. Clipboard history is a utility that stores recently copied data for easy pasting; it does not manage or enforce file access rules.

1. Arpaci-Dusseau, R. H., & Arpaci-Dusseau, A. C. (2018). Operating Systems: Three Easy Pieces. Arpaci-Dusseau Books. Chapter 39, Section 39.3, "Access Control," details how access control lists and permissions are used to mediate access to files.

2. Saltzer, J. H., & Schroeder, M. D. (1975). The Protection of Information in Computer Systems. Proceedings of the IEEE, 63(9), 1278–1308. Section I.A.1, "Controlling Access to Information," describes the basic principles of using access controls to protect information. https://doi.org/10.1109/PROC.1975.9939