What is the implication of this command?（）

• A、The command produces an error because the retention time cannot be reduced. 
• B、All historical data is retained but the subsequent flashback data archives are maintained for only three years. 
• C、All historical data is purged and the new flashback data archives are maintained for three years. 
• D、All historical data older than three years is purged from the flashback archive FLA1.