A technician investigates a server with an internal RAID 5 array that has been reported down. When looking at the console they find an error message stating: `Operating System not found'. Which of the

RAID 5 can only tolerate a single drive failure; if multiple hard drives crash, the array becomes unrecoverable, making the operating system inaccessible and causing a 'not found' error.

A network being unplugged would prevent network communication but would not cause an internal server to report 'Operating System not found' during the boot process.

Corruption of the master boot record (MBR) or partition table on the boot drive prevents the system's BIOS/UEFI from locating and loading the operating system, even if the underlying RAID array is functional.

A single hard drive crash in a RAID 5 array puts it in a degraded state, but the operating system should still be accessible and the server operational with reduced redundancy.

Leaving an OS install CD-ROM in the tray typically leads to a boot prompt from the CD-ROM or the installer, not an 'Operating System not found' error specifically related to the hard drive.