Oracle Active Data Guard Far Sync is specifically designed to provide zero-data-loss protection when the physical standby database is too geographically distant for direct synchronous redo transport without unacceptable primary-database latency.

The primary database sends redo synchronously to a nearby Far Sync instance. Because the Far Sync instance is positioned within low network latency of the primary, the primary can obtain the acknowledgement required for zero-data-loss protection without waiting for communication with the distant standby. Far Sync then forwards the redo asynchronously across the higher-latency interregional connection to the remote standby.

Oracle's Oracle Database@Azure reference architecture explicitly uses this pattern: the primary sends redo in SYNC mode to its local Far Sync instance, which forwards it in ASYNC mode to the remote standby database.

Maximum Performance using ASYNC alone permits a potential data-loss window. A snapshot standby is intended primarily for temporary read/write testing. Fast-Start Failover automates role transitions but requires an Observer and does not independently solve the synchronous-transport latency problem.

Therefore, C is correct. Study Guide reference: HA and DR — Active Data Guard Far Sync and zero-data-loss cross-region protection.

===============