Which type of trust policy should you create?

Your network contains an Active Directory forest named adatum.com. The forest contains an Active DirectoryRights Management Services (AD RMS) cluster.
A partner company has an Active Directory forest named litwareinc.com. The partner company does not have
AD RMS deployed.
You need to ensure that users in litwareinc.com can consume rights-protected content from adatum.com.
Which type of trust policy should you create?

A.
At federated trust

B.
A trusted user domain

C.
A trusted publishing domain

D.
Windows Live ID

Explanation:
A:
In AD RMS rights can be assigned to users who have a federated trust with Active Directory Federation
Services (AD FS). This enables an organization to share access to rights-protected content with another
organization without having to establish a separate Active Directory trust or Active Directory Rights
Management Services (AD RMS) infrastructure.
http://technet.microsoft.com/en-us/library/dd772651(v=WS.10).aspx
http://technet.microsoft.com/en-us/library/cc738707(v=WS.10).aspx
http://technet.microsoft.com/en-us/library/cc757344(v=ws.10).aspx