Why should you back up a duplicated tablespace after a TSPITR is complete？（）  

• A、 The tablespace cannot be duplicated or restored to any point in time after the duplication. 
• B、 The tablespace cannot be duplicated or restored to the point in time before the duplication. 
• C、 The entire database cannot be restored after a TSPITR， so a backup is required.
• D、 You cannot bring the tablespace online until its been backed up.
• E、 There is no requirement to do so， as RMAN will back up the tablespace after the TSPITR.