Which three reasons could be the cause of the failure?

A customer reported that during maintenance activity, some users were unable to connect to assigned desktops and received an error that the pool had no desktops available. Other users were able to connect to their assigned desktops without issue.

Which three reasons could be the cause of the failure? (Choose three.)
A . SQL Server was down.
B . VMware Composer Server was down.
C . View Connection Server was down.
D . vCenter Server was down.
E . App Volumes Manager Server was down.

Answer: CDE