What should you do?

You work as an enterprise administrator at Domain.com. The Domain.com network consists of a single Active Directory forest named us.Domain.com and uk.Domain.com.
The functional level of us.Domain.com is set at Windows Server 2008 and the functional level of uk.Domain.com is set at Windows Server 2003 Native Mode. During the course of the day you receive an instruction from management to have an external trust configured between us.Domain.com and uk.Domain.com. To ensure productivity throughout the organization you thus decide to have Kerberos AES encryption enabled.
What should you do?

A.
This can be accomplished by ensuring that the uk.Domain.com forest functional level is raised to Windows Server 2008.

B.
This can be accomplished by ensuring that the uk.Domain.com domain functional level is raised to Windows Server 2008.

C.
This can be accomplished by ensuring that the us.Domain.com forest functional level is raised to Windows Server 2008.

D.
This can be accomplished by ensuring that a new forest trust created and forest-wide authentication is enabled.