Your network contains an Active Directory forest. The forest contains a single domain.
You want to access resources in a domain that is located in another forest.
You need to configure a trust between the domain in your forest and the domain in the other
forest.
What should you create?

A.
an incoming external trust

B.
an incoming realm trust

C.
an outgoing external trust

D.
an outgoing realm trust

Explanation:
http://technet.microsoft.com/en-us/library/cc816877.aspx
A one-way, incoming, external trust allows users in your domain (the domain that you are
logged on to at the time that you run the New Trust Wizard) to access resources in another
Active Directory domain (outside your forest).