What does it mean if a backup is expired？（）  

• A、 The backup set has exceeded the retention criteria set in RMAN and is eligible for removal. 
• B、 The backup set has one or more invalid blocks in it and is not usable for recovery.
• C、 The backup set contains one or more tablespaces no longer in the database.
• D、 The backup set contains one or more missing backup set pieces.
• E、 The backup set is from a previous version of RMAN and was not upgraded.