Which type of backup involves saving all data every time changes occur?

The correct choice for the type of backup that involves saving all data every time changes occur is the snapshot backup. A snapshot backup captures the state of a system at a specific point in time, ensuring that all changes are saved whenever they happen. This type of backup is particularly useful for virtual machines or systems where continuous data protection is necessary, as it allows for quick restoration to various points in time without requiring a complete backup each time changes are made.

In contrast, a full backup saves all data at a particular moment but does not continuously track changes. Incremental backups only save changes made since the last backup, whether it was a full or incremental backup, making them efficient but not comprehensive at every interval. Differential backups save changes made since the last full backup but require that full backup as a reference, capturing more data over time as more changes accumulate. Understanding these distinctions helps in choosing the right backup strategy depending on data sensitivity and recovery time objectives.