Choice "C" is correct. An incremental backup involves copying only the data items that have changed since the last backup. This produces a set of incremental backup files, each containing the results of one day's transactions.
Choice "b" is incorrect. Differential backup copies all changes made since the last full backup.
Choice "a" is incorrect. Full Backup is an exact copy of the entire database.
Choice "d" is incorrect. Back up schedules are not routinely referred to as off-schedule backups. This is a distracter.
