In UNIX-like OS, the authority for a certain file varies depending on the user who uses it.
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In UNIX-like OS, the authority for a certain file varies depending on the user who uses it. Which of the following description is correct?
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UNIX file permissions follow a three-tier model: owner (user), group, and others (everyone else). Each file has exactly one owner and one group, with permissions (read, write, execute) independently set for each category. Option C accurately describes this three-category permission model. Options A and B incorrectly suggest multiple owners or that only owners have permissions, which contradicts UNIX's group and other permission concepts. Option D incorrectly states multiple owners/groups exist, which is not how UNIX filesystems work.
Step-by-step Derivation:
UNIX file permissions are represented as 'rwxrwxrwx' (9 bits): first 3 bits for owner, next 3 for group, last 3 for others. Example: 'chmod 755 file' sets owner=rwx, group=rx, others=rx. Each file has metadata (inode) storing: one uid (owner), one gid (group), and three permission sets. This architecture allows granular access control beyond just the file owner, making option C the complete and correct description.