An administrator is monitoring a High Availability (HA) and Distributed Resource Scheduler (DRS) enabled cluster and has noticed that virtual machines in the
cluster are being migrated without user intervention.
Why is this happening?

A.
The DRS Automation level is set to Fully Automated.

B.
The Automation level is set to Automatic.

C.
The DPM Threshold is set to Aggressive.

D.
The Power Management feature is configured.

Explanation:
When the DRS automation level is set to filly automated, virtual machines in the cluster might be migrated without user intervention.
http://www.uf-it.eu/Datenblaetter/VMware%20vsphere%20evaluators%20guide.pdf