I think the POSIX standard only has one root user, however many users can have root privileges.
So it's probably a trick question, however any user even without privilege can make create a file which others can't, read even the root itself I think not sure though.
There is only one root user. Other users may have root access though. Any user can create files only readable by them, but root user can override all of them, change password of any user etc. For a user having root access, they can do all sorts of things root user does