The following statements regarding centralized administration concepts are presented to you in an interview in which only one of them is correct. Which of these is correct?

A) Directory service is an XML standard that allows secure web domains to exchange user authentication and authorization data.
B) Extensible authentication protocol is a framework to transport authentication protocols.
C) The transport protocol used by RADIUS is TCP.
D) A RADIUS client can be defined as a desktop or a wireless laptop requesting authentication.