Which of the Following Operant Conditioning Techniques Is INCORRECTLY Paired

Which of the following operant conditioning techniques is INCORRECTLY paired with its description?

A) Token system-An individual is rewarded for desired behavior with such items as chips or play money,which he or she can exchange for desired items.
B) Contingency contracting-The therapist and client create a written agreement specifying the consequences for desirable and undesirable behaviors.
C) Observational learning-An individual models desired behavior for the client.
D) Token system-The therapist reduces the frequency of undesired behavior by pairing an aversive,unpleasant stimulus with undesired behavior.