The UNDO_RETENTION parameter in your database is set to 1000 and undo retention 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 every 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 UNDO tablespace for 1，000 seconds，then it gets moved to the TEMPORARY tablespace to provide read consistency.