Which two statements are true about undo segments and the use of undo by transactions in an Oracle database instance? AB A Undo segments can to the first extent when a transaction fills the last extend of the undo segment. B Undo segments can extend when a transaction fills the last extent of the undo segment. C A single transaction may use multiple undo segments simultaneously D Undo segments can be stored in the SYSTEM tablespace. E Undo segments can be stored in the SYSAUX tablespace.