Which infrastructure should you recommend?

Your company has three main offices named Main1, Main2, and Main3.
The network contains an Active Directory domain named contoso.com.
Each office contains a help desk group.
You plan to deploy Microsoft System Center 2012 Configuration Manager to meet the following
requirements:
The members of the Domain Admins group must be able to manage all of the Configuration
Manager settings.
The help desk groups must be able to manage only the client computers in their respective office by
using Configuration Manager.
You need to recommend a Configuration Manager infrastructure to meet the requirements.
Which infrastructure should you recommend? More than one answer choice may achieve the goal.
Select the BEST answer.

A.
Three sites that contain one collection for each office

B.
One site that contains one collection

C.
Three sites that each contain one collection

D.
One site that contains a collection for each office