Which files must be synchronized in order for a database to start？（）

A.Damaged or lost data files are restored from backups.
B.Redo log file entries are used to roll forward the database.
C.Undo segments are used to roll back any uncommitted transactions.
D.Transactions that were active when the failure occurred are restarted.
E.Transactions that were active when the failure occurred are automatically committed during the recover procedure.

A.Only the damaged or lost data files.
B.All of the data files of the database.
C.Only the data files belonging to the SYSTEM tablespace.
D.The data files belonging to the SYSTEM tablespace and the damaged or lost data files.