You deploy System Center 2012 Operations Manager.
You create two unsealed management packs named MP1 and MP2.
You create an override for MP1.
You create a group in MP2.
You need to apply the override for MP1 to the group in MP2.
What should you do before you apply the override?

A.
Create a new class in MP2.

B.
Seal MP1.

C.
Seal MP2.

D.
Create a new class in MP1.

Explanation:
When you create a group, you save it to an unsealed management pack.
However, an element in an unsealed management pack, such as a group, cannot reference an
element in a different unsealed management pack, such as an override or a view.
If you are going to use a group to target an override or scope a view, you must either save the group
to the same unsealed management pack as the override or view, or you must seal the management
pack that contains the group.
If you save the group to the same unsealed management pack as the override or view, you can only
use that group for overrides and views that are also contained in that unsealed management pack.
If you seal the management pack that contains the group, you can reference that group from other
unsealed management packs.

However, you cannot easily change any group settings in the sealed management pack or add new
groups to the sealed management pack.
http://www.code4ward.net/main/Blog/tabid/70/EntryId/130/Implications-when-using-groups-froma-sealed-MPfor-overrides.aspx