Decreased employee productivity after data loss is most directly caused by lack of data backup. If business data stored or accessed through mobile devices is lost and cannot be restored, employees may need to recreate work, delay tasks, repeat transactions, or wait for recovery. Malware, sensitive data exposure, and lack of encryption are serious security and privacy concerns, but they do not directly explain productivity loss from unrecoverable data. Backup controls support availability and recovery by ensuring data can be restored after deletion, corruption, device theft, or system failure. Internal auditors should evaluate mobile backup requirements, synchronization, cloud storage controls, recovery testing, encryption, and incident response.
Therefore, Option D is correct.