You need to ensure that the G_Marketing members can access the folder from the network

Your network contains two Active Directory forests named contoso.com and nwtraders.com.
A two-way forest trust exists between contoso.com and nwtraders.com. The forest trust is
configured to use selective authentication.
Contoso.com contains a server named Server1. Server1 contains a shared folder named
Marketing.
Nwtraders.com contains a global group named G_Marketing. The Change share permission
and the Modify NTFS permission for the Marketing folder are assigned to the G_Marketing
group. Members of G_Marketing report that they cannot access the Marketing folder.
You need to ensure that the G_Marketing members can access the folder from the network.
What should you do?

A.
From Windows Explorer, modify the NTFS permissions of the folder.

B.
From Windows Explorer, modify the share permissions of the folder.

C.
From Active Directory Users and Computers, modify the computer object for Server1.

D.
From Active Directory Users and Computers, modify the group object for G_Marketing.

Explanation:
MS Press – Self-Paced Training Kit (Exam 70-640) (2nd Edition, July 2012) page 643-644

After you have selected Selective Authentication for the trust, no trusted users will be able to
access resources in the trusting domain, even if those users have been given permissions.
The users must also be assigned the Allowed To Authenticate permission on the computer
object in the domain.
To assign this permission:
1. Open the Active Directory Users And Computers snap-in and make sure that Advanced
Features is selected on the View menu.
2. Open the properties of the computer to which trusted users should be allowed to
authenticate—that is, the computer that trusted users will log on to or that contains
resources to which trusted users have been given permissions.
3. On the Security tab, add the trusted users or a group that contains them and select the
Allow check box for the Allowed To Authenticate permission.