A system administrator needs to upgrade the Oracle database from Version 7 to Version 8.  Which of the following scheduling concerns should be considered?（）

• A、Schedule enough down time to backup, upgrade and reboot. 
• B、Backup, upgrade, then schedule enough down time to reboot the system.
• C、Backup, then schedule enough down time to upgrade and reboot the system. 
• D、There are no scheduling concerns because no down time is required.