Your company has a private cloud that is managed by using a System Center 2012 infrastructure.
The network contains an Operations Manager infrastructure and a Virtual Machine Manager (VMM)
infrastructure.
The private cloud contains a clustered VMM solution that has two virtualization hosts.
The VMM solution hosts seven virtual machines.
The virtual machines are configured as shown in the following table.

You configure Dynamic Optimization to use the following settings:
A CPU Dynamic Optimization threshold of 30 percent
A CPU host reserve threshold of 15 percent
Low aggressiveness
You monitor the VMM solution and discover that the virtual machines rarely migrate from Server1
to Server2 when CPU utilization exceeds the configured threshold.
You need to increase the likelihood of the virtual machines migrating from Server1 to Server2 when
CPU utilization exceeds the configured threshold.
What should you do?

A.
set the Aggressiveness to High.

B.
Enable Power Optimization.

C.
Configure a host profile.

D.
Modify the CPU host reserve threshold.

Explanation:
http://blogs.technet.com/b/scvmm/archive/2011/05/04/dynamic-optimization-andpoweroptimization-in-scvmm-2012.aspx
Good post here:

What have you configured regarding the dynamic optimization? How aggressive is the treshold for
optimizing your cluster? First of all, you must check the option “Automatically migrate virtual
machines to balance load”.
Second, specify how aggressive the optimization should be.
The more agressive, the more likely to live migrate VMs even for small gain.
Last, you can also configure the resource treshold for when optimization should kick in.
Default it`s set to 30% CPU and 512 MB RAM.
To test and verify, right click on your cluster, and click “optimize hosts”.
VMM will check if it`s anything to gain, on demand, and eventually live migrate VMs to balance the
load.
http://social.technet.microsoft.com/Forums/enUS/virtualmachingmgrhyperv/thread/45dfd50da2a4-4a7a-9c88-53fd7cedda77