Your company has two main offices in Denver and Chicago and four branch offices in New York, Miami, Seattle, and San Francisco.

Each office is configured as an Active Directory site. Site links are configured as shown in the exhibit.
The network consists of one Active Directory forest.

All domain controllers run Windows Server 2003.

Each main office has four domain controllers. Each branch office has one domain controller. The Bridge all site links option is disabled.

You need to prepare the environment to install a read-only domain controller (RODC) in each branch office. The solution must be achieved by upgrading the minimum number of domain controllers.
What should you do?

Exhibit:

A.
Upgrade one domain controller in the Chicago office and one domain controller in the Denver office to Windows Server 2008.

B.
Upgrade one domain controllers in the Chicago office to Windows Server 2008. Create a site link that connects the Seattle and San Francisco office sites to the Chicago office site.

C.
Configure a site link to connect all branch office sites. Upgrade one domain controller in the Denver office to Windows Server 2008.

D.
Configure a site link to connect the Chicago office site and the San Francisco and Seattle office sites.
Upgrade one domain controller in the Denver office to Windows Server 2008.