A.You should consider creating a database availability group (DAG). Then a backup of the mailbox database file should be restored. Thereafter the Export-Mailbox cmdlet should be run.
B.You should consider creating a new Mailbox Recovery Database. Then a backup of the database file should be restored. Thereafter the Export-Mailbox cmdlet should be run.
C.You should consider creating a new Mailbox Recovery Database. Then a backup of the database file should be restored. Thereafter the Restore-Mailbox cmdlet should be run.
D.You should consider creating a database availability group (DAG). Then a backup of the mailbox database file should be restored. Thereafter the Restore-Mailbox cmdlet should be run.