One of the user sessions was terminated abnormally in the middle of a transaction. What does Oracle database do to recover it？（）

A.uses undo data for roll forward

B.uses Flashback Log for recovery

C.uses online redo logs to roll back

D.uses undo data to roll back the transaction

E.uses Recovery Manager （RMAN） to roll back

F.uses the System Monitor （SMON） background process to perform instance recovery