Your network contains two Active Directory forests. The forests contain domain controllers that run
Windows Server 2008 R2. The forests are configured as shown in the following table.

A one-way forest trust exists from adatum.com to litwareinc.com. You plan to deploy an Exchange
Server 2010 Service Pack 1 (SP1) organization. The organization will contain Mailbox servers in
litwareinc.com. You need to ensure that users in adatum.com can access the mailboxes in the
Exchange organization. What should you do?

A.
Create a forest trust from litwareinc.com to adatum.com. Create linked mailboxes in
litwareinc.com.

B.
Create a forest trust from litwareinc.com to adatum.com. Create resource mailboxes in
litwareinc.com.

C.
Change the forest trust to an external trust. Create linked mailboxes in litwareinc.com.

D.
Deploy Mailbox servers to adatum.com. Create resource mailboxes in litwareinc.com.

Explanation:
Linked mailboxes are user mailboxes that are accessed by users in a separate, trusted forest
http://forums.msexchange.org/m_1800450025/mpage_1/key_/tm.htm#1800553199