Your company, Contoso Ltd, has offices in North America and Europe. Contoso has an
Active Directory forest that has three domains.
You need to reduce the time required to authenticate users from the labs.eu.contoso.com
domain when they access resources in the eng.na.contoso.com domain.
What should you do?

A.
Decrease the replication interval for all Connection objects.

B.
Decrease the replication interval for the DEFAULTIPSITELINK site link.

C.
Set up a one-way shortcut trust from eng.na.contoso.com to labs.eu.contoso.com.

D.
Set up a one-way shortcut trust from labs.eu.contoso.com to eng.na.contoso.com.

Explanation:
http://technet.microsoft.com/en-us/library/cc754538.aspx
Understanding When to Create a Shortcut Trust
When to create a shortcut trust
Shortcut trusts are one-way or two-way, transitive trusts that administrators can use to
optimize the authentication process.
Authentication requests must first travel a trust path between domain trees. In a complex
forest this can take time, which you can reduce with shortcut trusts. A trust path is the series
of domain trust relationships that authentication requests must traverse between any two
domains. Shortcut trusts effectively shorten the path that authentication requests travel
between domains that are located in two separate domain trees.
Shortcut trusts are necessary when many users in a domain regularly log on to other
domains in a forest.
Using the following illustration as an example, you can form a shortcut trust between domain
B and domain D, between domain A and domain 1, and so on.

Using one-way trusts
A one-way, shortcut trust that is established between two domains in separate domain trees
can reduce the time that is necessary to fulfill authentication requests—but in only one

direction. For example, when a oneway, shortcut trust is established between domain A and
domain B, authentication requests that are made in domain A to domain B can use the new
one-way trust path. However, authentication requests that are made in domain B to domain
A must still travel the longer trust path.
Using two-way trusts
A two-way, shortcut trust that is established between two domains in separate domain trees
reduces the time that is necessary to fulfill authentication requests that originate in either
domain. For example, when a two-way trust is established between domain A and domain B,
authentication requests that are made from either domain to the other domain can use the
new, two-way trust path.