Comprehensive and Detailed Explanation From Exact Extract of Enterprise Firewall 7.6 Administrator documents:
Based on the FortiOS 7.6 Administration Guide and the HA Virtual Clustering documentation, the exhibit demonstrates a Virtual Clustering environment where multiple VDOMs are distributed across an HA cluster.
In a virtual cluster setup, VDOMs are assigned to either virtual cluster 1 (vcluster 1) or virtual cluster 2 (vcluster 2). Each virtual cluster has its own independent primary unit selection process. The primary unit for a virtual cluster is determined based on the standard HA selection criteria: Monitored Interfaces > HA Uptime > Priority > Serial Number.
According to the exhibit:
Virtual Cluster 1 (edit 1) contains VDOMs "Core1" and "root".
Virtual Cluster 2 (edit 2) contains VDOM "Core2".
The HA uptime is stated to be the same for both devices.
For edit 2 (Core2), HQ-NGFW-1 has a priority of 150, while HQ-NGFW-2 has a priority of 120.
In both units, override is disabled (default).
Since the uptime is equal and no monitored interfaces are down, the cluster uses the Priority value to select the primary unit for each vcluster. Currently, HQ-NGFW-1 is the primary for Core2 because its priority (150) is higher than HQ-NGFW-2's (120). To ensure HQ-NGFW-2 handles the Core2 traffic, its priority for virtual cluster 2 must be increased to a value higher than 150. Option C (changing the priority from 120 to 200) achieves this.