This is the correct answer because these are the four folders that normally appear at the root level of the storage volume in the Finder on a Mac. The root level is the topmost level of the filesystem hierarchy, denoted by /. The Applications folder contains all the applications installed on the Mac, the Library folder contains system and user preferences, the System folder contains the operating system files, and the Users folder contains the home folders of each user account. These folders are essential for the functioning and organization of the Mac, and they should not be modified or deleted without a good reason.  References :  Access the Root Directory in Mac OS X in 4 Ways Quickly ,  Unix filesystem - Wikipedia ,  Working with APFS Volume Groups | Carbon Copy Cloner - Bombich