You issued the RMAN>SHOW ALL； command. The output of this command is as follows： After analyzing the output， which conclusion will you draw？（）

• A、 The current control file is not automatically backed up every time you perform a backup.
• B、 The backups save space on the storage media.
• C、 While performing backups across a network， the network bandwidth is reduced.
• D、 The backups consist of backup pieces.