Final answer:
The command "config system ha set link-failed-signal enable end" performs configures the system to signal link failure. Thus option C is correct.
Step-by-step explanation:
In a High Availability (HA) setup for a firewall system, maintaining communication between the primary and secondary units is crucial. The "link-failed-signal" parameter is related to signaling when there is a failure in the communication link between the primary and secondary units. Enabling this option ensures that the system is configured to send a signal or notification in the event of a link failure. This signaling is an essential aspect of HA configurations, allowing the system to respond appropriately to changes in the network