Your database instance is running with full workload after database creation. You have decided to useafixed-sizeundo tablespace. You want to use the Undo Advisor to estimate the capacity of the undotablespace. 
Which two factors must you consider before using the Undo Advisor to estimate the capacity of the undotablespace（）

A.It is the time period after which the undo data becomes obsolete.
B.It is the time period after which the committed undo data would be transferred to a temporarytablespace.
C.It is the minimum time period up to which the committed undo data would be retained if free undo spaceis available.
D.It is the time period after which the undo data is transferred to the Flash Recovery Area to provide readconsistency.

A.when the data file of the undo tablespace is autoextensible
B.when there are more than one undo tablespaces available in the database
C.when the undo tablespace is of a fixed size and retention guarantee is not enabled
D.when the undo tablespace is autoextensible and retention guarantee is not enabled

A.The extents in the undo tablespace retain data until the next full database backup.
B.The extents containing committed undo in the undo tablespace are not overwritten for at least 15minutes.
C.The extents containing committed data in the undo tablespace are not overwritten until the instance isshut down.
D.The extents containing committed undo in the undo tablespace are transferred to Flash Recovery Areabefore being overwritten.