A BIG-IP Administrator makes a configuration change to a Virtual Server on the Standby device of an HA pair. The HA pair is currently configured with Auto-Sync Enabled. What effect will the change hav

This choice is partially correct as the change will be effectively undone, but the phrasing of D implies the active config propagating is the 'effect' of auto-sync.

Auto-Sync propagates changes from the active device to the standby device, not from the standby to the active, especially when the standby's configuration diverges.

Similar to A, this describes the outcome that the change is lost, but the question asks about the effect of Auto-Sync propagating the config to the HA pair, which will result in the active config prevailing.

When Auto-Sync is enabled on a BIG-IP HA pair, the active device is the authoritative source for the configuration. If a change is made directly on the standby device, the subsequent automatic synchronization from the active device will propagate the active's configuration, which then "takes effect" across the HA pair by overwriting any differing local changes on the standby unit.