Which description of HA on the 1000v is true?

While redundancy is indeed provided by a standby VSM, stating they are 'in a HA State' (option C) is a more complete and accurate description of the operational mode, encompassing the synchronization aspect.

The Nexus 1000V VSMs operate in an active-standby configuration, not a dual-active configuration, to prevent potential conflicts and ensure consistent control plane operation.

The Cisco Nexus 1000V provides High Availability (HA) through a redundant pair of Virtual Supervisor Modules (VSMs), which operate in an active-standby state. The active VSM manages the virtual switch, while the standby VSM continuously synchronizes its state with the active VSM. This synchronization ensures that if the active VSM fails, the standby VSM can seamlessly take over, minimizing service disruption.

If the VSMs are in an HA state, they are by definition synchronized or actively synchronizing; being 'not yet synchronized' implies they are not fully operational in an HA configuration.