Explanation/Reference:
Explanation:
C: Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. You must have already enabled Flashback Database on the original primary database before the failover.
D: Block media recovery is a technique for restoring and recovering corrupt data blocks while data files are online. If only a few blocks are corrupt, then block media recovery may be preferable to data file media recovery. For automatic block media recovery to work, a physical standby database must be in real-time query mode, which requires an Oracle Active Data Guard license.
References:
https://docs.oracle.com/cd/E11882_01/server.112/e41134/scenarios.htm
https://docs.oracle.com/database/121/BRADV/rcmblock.htm#BRADV89786