Which terminology is being described below?

Which terminology is being described below?
These trusts are sometimes necessary when users need access to resources that are located in a Windows
NT 4.0 domain or in a domain that is in a separate Active Directory Domain Services (AD DS) forest that is not
joined by a forest trust.

A.
Shortcut Trusts

B.
Realm Trusts

C.
Forest Trusts

D.
External Trust

Explanation:
You can create an external trust to form a one-way or two-way, nontransitive trust with domains that are outside
your forest http://technet.microsoft.com/enus/library/cc775736%28v=ws.10%29.aspx Trust types

http://technet.microsoft.com/en-us/library/cc731297.aspxUnderstanding When to Create a Realm Trust When to create a realm trust You can establish a realm trust
between any non-Windows Kerberos version 5 (V5) realm and an Active Directory domain. This trust
relationship allows cross-platform interoperability with security services that are based on other versions of the
Kerberos V5 protocol, for example, UNIX and MIT implementations. Realm trusts can switch from non transitive
to transitive and back. Realm trusts can also be either one-way or two way.