Which definition best defines what a challenge-response session is?

A.
A challenge-response session is a workstation or system that produces a random login ID that
the user provides, when prompted, in conjunction with the proper PIN (Personal Identification
Number).

B.
A challenge-response session is a workstation or system that produces a random challenge
string that the user provides, when prompted, in conjunction with the proper PIN (Personal
Identification Number).

C.
A challenge-response session is a special hardware device used to produce random text in a
cryptography system.

D.
A challenge-response session is the authentication mechanism in the workstation or system
that does not determine whether the owner should be authenticated.

Explanation:

A common authentication technique whereby an individual is prompted (the challenge) to provide
some private information (the response). Most security systems that rely on smart cards are based
on challenge-response. A user is given a code (the challenge) which he or she enters into the
smart card. The smart card then displays a new code (the response) that the user can present to
log in.
Reference:
http://www.webopedia.com/TERM/C/challenge_response.html