Which of the following conditions could prevent HA from powering on a virtual machine
(Choose Two)?

A.
The VM has a low priority setting

B.
Strict admission control is configured

C.
The target host is not compatible with the virtual machine

D.
The VM is connected to the ESX Host CD-ROM drive

Explanation:
vSphere Availability Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 13.
Admission control imposes constraints on resource usage and any action that would
violate these constraints is not permitted. Examples of actions that could be disallowed
include:
Powering on a virtual machine.
Migrating a virtual machine onto a host or into a cluster or resource pool.
Increasing the CPU or memory reservation of a virtual machine.

vSphere Availability Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 22.
VM restart priority determines the relative order in which virtual machines are restarted
after a host failure. Such virtual machines are restarted sequentially on new hosts, with
the highest priority virtual machines first and continuing to those with lower priority until
all virtual machines are restarted or no more cluster resources are available.