An administrator wants to ensure a server OS and data can be recovered in case all the server's hard disk drives fail simultaneously. Which of the following backup types must be implemented to meet…

A full backup copies every file on the system, including OS files and all data, at a single point in time, making it entirely self-sufficient for restoration. Because it has no dependency on any prior backup set, it is the only backup type that alone can restore a server to a known good state after catastrophic drive loss.

A differential backup only stores files changed since the last full backup, so it cannot stand alone and requires a prior full backup to perform a complete restore.

An incremental backup only records changes since the most recent backup of any type, requiring the full backup plus every incremental in the chain to reconstruct the system.

Bare metal describes the target restore environment - new hardware with no OS installed - not a backup classification; the underlying backup that feeds a bare metal restore is still a full or image-based backup.