Before a Flashback Table operation，you execute the following command：   ALTER TABLE employees ENABLE ROW MOVEMENT；   Why would you need this to be executed？（）  

A.Because row IDs may change during the flashback operation

B.Because the object number changes after the flashback operation

C.Because the rows are retrieved from the recycle bin during the flashback operation

D.Because the table is moved forward and back to a temporary during the flashback opertion