When automatic backup retention of a DB system is disabled,deleting the DB system(Answer C) will delete all automatic backups of the DB system.
* Automatic Backups: These are backups created automatically by the OCI service to ensure data protection.
* Backup Deletion: If automatic backups are disabled and you delete the DB system, all associated automatic backups are also deleted. This operation is irreversible, and you should ensure that necessary backups are taken before deleting the DB system.
References:
* OCI MySQL Database Service Backup and Restore

To determine the version of MySQL running on your DB system, you can use the following SQL statements:
* SELECT @@version;(Answer B): This query retrieves the MySQL server version from the system variables.
* SHOW VARIABLES LIKE 'version';(Answer C): This query displays the server version along with other related version variables.
Steps:
* Connect to your MySQL DB system.
* Execute eitherSELECT @@version;orSHOW VARIABLES LIKE 'version';to retrieve the version information.
References:
* MySQL Server Version Information
* SHOW VARIABLES Syntax

Two methods to import data into a MySQL DB system using MySQL Shell are:
A:util.importTable(): This utility imports data from a file into a table. D.util.loadDump(): This utility loads a previously dumped database or table into a MySQL DB system.

The error message indicates that the source has purged required binary logs, making it impossible to replicate the missing transactions. This happens when the administrator manually deletes binary log files from the source DB system, or the binary log expiration period is too short, causing automatic purging before the replica can fetch the transactions.

When high availability is enabled for a stand-alone DB system,the DB system has three instances running in different availability or fault domains(Answer D).
* High Availability Configuration: This setup involves creating multiple instances of the DB system across different availability or fault domains to ensure redundancy and minimize the risk of downtime due to hardware or network failures.
* Instances: Typically, there are three instances-one primary and two replicas-ensuring that the system can failover seamlessly if one instance goes down.
References:
* OCI MySQL High Availability