A copy of files and programs made to facilitate recovery if necessary. Response:

A backup is a fundamental data protection measure involving making duplicate copies of data, applications, and operating system configurations. These copies are stored separately and are used to restore systems or data to a previous state in the event of data loss, corruption, or system failure, directly matching the definition.

Delete means to remove data or files permanently, which is the opposite of making a copy for recovery.

Retire refers to the process of formally removing a system or asset from service, not making copies for recovery.

'None of these' is incorrect because 'Backup' is the correct term.