You are employed as a developer at ABC.com. ABC.com has a single Active Directory domain,
named ABC.com.
You are running a training exercise for junior developers. You are currently discussing something
that defines the requirements that apps must meet to participate in distinctive Windows 8
interactions.
Which of the following is being discussed?

A.
Charms

B.
Extensions

C.
Contracts

D.
Live tiles

Explanation:
http://msdn.microsoft.com/en-us/library/windows/apps/hh464906.aspx