You are working on a 24X7 database. You want to design a backup strategy for your database that uses user managed backups. You want to be able to perform all backups while the database remains online. 
Which statement about performing user-managed backups in a 24x7 environment is true？（）

A. The data file is checked for physical corruption and backed up if found clean.
B. The backup of data file 5 is performed and the interactive messages during the backup are suppressed.
C. The existing backup for the data file is checked and the backup is performed if there are changes in the data file after the last backup.
D. The backup of data file 5 is performed and all SQL statements that are executed during RMAN compilation and their results are displayed

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

A. generating the SQL profile
B. testing and accepting the SQL profile
C. generating a list of candidate SQLs for tuning
D. adding tuned SQL plans into the SQL plan baseline
E. tuning each SQL statement in the order of importance 
F. generating baselines that include candidate SQLs for tuning