（12）You performed the RMAN database backup having a backupset key number 231 with the KEEP FOREVER option.

After some days,you want to change the status of the database backup and you issued the following command:

RMAN>CHANGE BACKUPSET 231 NOKEEP;

What is the implication of this command?

A. The backup is deleted.

B. The backup is marked unavailable.

C. The backup overrides the backup retention policy.

D. The backup becomes eligible for deletion according to the existing retention policy