（单选题）What does&#

题目描述

AThe backup set has exceeded the retention criteria set in RMAN and is eligible for removal. 

BThe backup set has one or more invalid blocks in it and is not usable for recovery. 

CThe backup set contains one or more tablespaces no longer in the database.  

DThe backup set contains one or more missing backup set pieces.

EThe backup set is from a previous version of RMAN and was not upgraded.