Your company, Contoso Ltd, has offices in North America and Europe.
Contoso has an Active Directory forestthat 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 thepath
that authentication requests travel between domainsthat 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, whena one-way,
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 thetime
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.