Which prerequisite must be met before accomplishing the backup?

Examine the RMAN command: RMAN> CONFIGURE ENCRYPTION FOR DATABASE ON;
RMAN> BACKUP DATABASE PLUS ARCHIVELOG; Which prerequisite must be met
before accomplishing the backup?

A.
Oracle wallet for the encryption must be set up.

B.
All the tablespaces in the database must be encrypted.

C.
The password for the encryption must be set up.

D.
Oracle Database Vault must be enabled.