Examine the query and its output:
What might have caused three of the alerts to disappear?
A. The threshold alerts were cleared and transferred to d0A_alert_history.
B. An Automatic Workload Repository (AWR) snapshot was taken before the execution of the second
C. An Automatic Database Diagnostic Monitor (ADOM) report was generated before the execution of the second query.
D. The database instance was restarted before the execution of the second query.