which of the following?

A network administrator uses an RFID card to enter the datacenter, a key to open the server rack, and a username and password to logon to a server. These are
examples of which of the following?

A.
Multifactor authentication

B.
Single factor authentication

C.
Separation of duties

D.
Identification

Explanation:
Single-factor authentication (SFA) is a process for securing access to a given system by identifying the party requesting access via a single category of credentials.
In this case, the network administrator makes use of an RFID card to access the datacenter, a key to access the server rack, and a username and password to
access a server.
Incorrect Answers:
A: Multifactor authentication requires a user to provide two or more authentication factors in order to access a given system.
C: Separation of duties divides administrator or privileged tasks into separate groupings, which in turn, is individually assigned to unique administrators.
D: Identification only proves who the user is, it will not give access.

Stewart, James Michael, CompTIA Security+ Review Guide, Sybex, Indianapolis, 2014, pp 275, 276, 282.
http://searchsecurity.techtarget.com/definition/single-factor-authentication-SFA