Final answer:
When HA is enabled in a vSphere environment, the service that starts on member hosts is the Fault Domain Manager (FDM).
Step-by-step explanation:
When HA (High Availability) is enabled in a vSphere environment, the service that starts on the member hosts is A) FDM (Fault Domain Manager). The Fault Domain Manager is responsible for monitoring the state of member hosts within a cluster and managing the process of restarting virtual machines on alternative hosts in case one of the member hosts fails. This ensures continuous availability and minimal disruption to services.