Your network contains an Active Directory forest. The forest contains two domains named contoso.com and
fabrikam.com. The functional level of the forest is Windows Server 2003.
You have a domain outside the forest named adatum.com.
You need to configure an access solution to meet the following requirements:
Users in adatum.com must be able to access resources in contoso.com.
Users in adatum.com must be prevented from accessing resources in fabrikam.com.
Users in both contoso.com and fabrikam.com must be prevented from accessing resources in adatum.com.
What should you create?

A.
a one-way realm trust from contoso.com to adatum.com

B.
a one-way realm trust from adatum.com to contoso.com

C.
a one-way external trust from contoso.com to adatum.com

D.
a one-way external trust from adatum.com to contoso.com

Explanation:
Users in adatum.com must be able to access resources in contoso.com.
Contoso needs to trust adatum.
We create a one-way external trust from contoso to adatum.