Which of the following permissions would enable users to modify files or directories on a server?

To modify files or directories on a server, users need the appropriate permissions that allow for changes to be made to the content within those files or directories. The permission that specifically permits users to make such modifications is the "Write" permission. This allows users to create new files, delete existing files, and make changes to the contents of files.

While "Read" permissions allow users to view files or directories, they do not enable any modifications. "Execute" permissions relate to running executable files or scripts rather than changing their contents. "Access" is not a standard permission in most permission schemes and may refer to the general ability to view or interact with a resource but does not inherently imply modification capability. Therefore, the "Write" permission is essential for users who need to alter files or directories on a server.