You work as a database administrator for Certkiller .com. The UNDO_RETENTION parameter in your database is set to 1000 and undoretention is not guaranteed. Which statement regarding retention of undo data is correct？（）

• A、Undo data becomes obsolete after 1，000 seconds.
• B、Undo data gets refreshed after 1，000 seconds.
• C、Undo data will be stored permanently after 1，000 seconds.
• D、Committed undo data would be retained for 1，000 seconds if free undo space is available.
• E、Undo data will be retained in the UNDOtablespacefor 1，000 seconds， then it gets movedmovedto the TEMPORARYtablespaceto provide read consistency.