To ensure data is unrecoverable on a lost or stolen mobile device, the best solution is:

Remote wipe: This feature allows the device owner or IT administrator to remotely erase all data on the device, ensuring that it cannot be recovered by unauthorized users.

Device encryption: While important for protecting data, encryption alone does not remove data from the device.

Data backup: Ensures data is saved elsewhere but does not make it unrecoverable on the lost or stolen device.

Fingerprint reader: Provides security for accessing the device but does not affect data recovery if the device is compromised.