You wish to revoke write access for all groups and named users on a file. Which command will make the correct ACL changes?

The `-x` option is used to remove specific ACL entries, not to modify the permissions of existing entries or the mask itself.

The `-x` option would attempt to remove the mask entry entirely, rather than modifying its permissions to `rx`.

The `setfacl -m` command is used to modify an existing ACL entry, and setting `mask::rx` effectively removes write permission for all named users, named groups, and the owning group, as the mask defines the maximum permissions these entries can have.

While `-m` is for modifying, specifying `group:*:rx,user:*:rx` is not the correct syntax or method to universally revoke write access by manipulating the mask; the mask entry itself should be targeted.