Final answer:
The answer is option B. The backup system that backs up all of the files that have changed since the last full backup is the Incremental backup system.
Step-by-step explanation:
The backup system that backs up all of the files that have changed since the last full backup is the Incremental backup system. In an incremental backup, only the files that have been modified or created since the last full backup are backed up. This helps to save storage space and reduces the time required for backups. However, in order to restore the data, you would need the original full backup and all subsequent incremental backups.