Which are the correct steps， in order， to deal with the loss of an online redo log if the database has not yet crashed？（）  
a. Issue a checkpoint. 
b. Shut down the database. 
c. Issue an alter database open command to open the database. 
d. Startup mount the database. 
e. Issue an alter database clear logfile command. 
f. Recover all database datafiles.

You have discovered that one of three control files has been lost. What steps would you follow to recover that control file？（）  
a. Shut down the database. 
b. Restore a control-file copy from backup media. 
c. Use the create control file command to create a new control file. 
d. Copy the backup control file into place. 
e. Create a new copy of the control file from one of the surviving control files. 
f. Recover the database using the recover database using backup control file command. 
g. Start up the database. 

You have lost all your SYSTEM tablespace datafiles （system_01.dbf and system_02.dbf） nd the database has crashed. 
What would be the appropriate order of operations to correct the situation？（）  
a. Mount the database with the startup mount command. 
b. Take the SYSTEM datafile offline with the alter database command. 
c. Restore the SYSTEM_01.dbf datafile from backup media with the required archived redo logs. 
d. Restore all SYSTEM tablespace-related datafiles from backup media.
e. Issue the recover tablespace SYSTEM command. 
f. Issue the recover datafile SYSTEM_01.dbf command. 
g. Open the database with the alter database open command. 
h. Open the database with the alter database open resetlogs command.