Which is a best practice for High Availability (HA) in an Exadata environment?

Which is a best practice for High Availability (HA) in an Exadata environment?

A.
Checksums performed on the Exadata Storage Server ensure logical consistency of block
content.

B.
When a standby database is in place, DB_BLOCK_CHECKING is not required and thus not
recommended.

C.
Oracle Exadata Storage Server Software HARD checks operate transparently after enabling
DB_BLOCK_CHECKSUM on a database.

D.
Due to the different architecture that Exadata has with storage servers, compared to regular
Storage Area Network, DB_LOST_WRITE_PROTECT need not be set.

E.
Stretched RAC is the best alternative for Exadata that combines both HA and DR into one.

Explanation:
Exadata storage cells include Oracle Hardware Assisted Resilient Data (HARD) to
provide a
unique level of validation for Oracle block data structures such as data block address, checksum.
and magic numbers prior to allowing a write to physical disks. HARD validation with Exadata is
automatic (setting DB_BLOCK_CHECKSUM is required to enable checksum validation). The
HARD checks transparently handle all cases including Oracle ASM disk rebalance operations and
disk failures.
Incorrect:
Not A: The checksum is used to validate that a block is not physically corrupt, detecting
corruptions caused by underlying disks, storage systems, or I/O systems. Checksums do not
ensure logical consistency of the block contents.
Not B: MAA recommends that you set DB_BLOCK_CHECKING=MEDIUM or FULL on the
physical standby as a minimum practice to prevent the standby from various logical block
corruptions.
Not D: The recommendation is:
On the primary database: DB_LOST_WRITE_PROTECT=TYPICAL (default TYPICAL on
Exadata) On the Data Guard Physical Standby Database:
DB_LOST_WRITE_PROTECT=TYPICAL Not E: Protection from a broad range of, but not all
disasters
While not a full disaster recovery (DR) solution, an Extended Distance
Oracle RAC or Oracle RAC One Node deployment will provide protection from a broad range of
disasters. For a full DR protection Oracle recommends deploying an Oracle RAC together with a
local and a remote Oracle Data Guard setup as described in the Maximum Availability Architecture
(MAA).