What does the DB_FLASHBACK_RETENTION_TARGET parameter configure?（）

• A、An upper limit on how far you can flash back the database, depending on the information in the redo logs
• B、An upper limit on how far you can flash back the database, depending on the information in the undo tablespace
• C、The amount of time for which the flashback data is to be kept in the flash recovery area, provided that there is enough space
• D、The amount of time for which the flashback data is guaranteed to be kept in the undo tablespace, provided that there is enough space