Which two statements are true with respect to the maintenance window？（） .

• A、 A DBA can enable or disable an individual task in all maintenance windows.
• B、 A DBA cannot change the duration of the maintenance window after it is created.
• C、 In case of a long maintenance window，all Automated Maintenance Tasks are restarted every four hours.
• D、 A DBA can control the percentage of the resource allocated to the Automated Maintenance Tasks in each window