Which two statements are true regarding Health Monitor checks in Oracle Database 11g？（）  

• A、 Health Monitor checks can be used to scan the contents of the redo log and archive logs for accessibility and corruption.
• B、 Health Monitor checks can be used to verify the integrity of database files and report failures if these files are inaccessible，corrupt or inconsistent.
• C、 Health Monitor checks can be used to verify the contents of dictionary entries for each dictionary object and fix it automatically.
• D、 Health Monitor checks are always initiated manually when there is some critical error.