Which backup type backs up only the changes since the last full backup?

• A. Full backups
• B. Incremental backups
• C. Differential backups
• D. Snapshot backups

Answer: (C)

Understanding how backup types track changes is what this question tests. A differential backup copies only the data that has changed since the last full backup. It uses the most recent full backup as the baseline and collects all changes that occurred after that baseline, so the differential backup grows bigger the longer you go between full backups. To restore, you need the last full backup plus the latest differential.

This differs from incremental backups, which store only what changed since the previous backup of any type (the last incremental or the last full), creating a chain for restoration that requires every increment since the last full. Full backups copy everything every time, regardless of changes. Snapshot backups capture the system state at a specific moment, not specifically the set of changes since the last full backup.