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.