Which of These Operant Conditioning Techniques Is CORRECTLY Paired with Its

Which of these operant conditioning techniques is CORRECTLY paired with its description?

A) token system-an individual is rewarded for desired behaviour with such items as chips or play money,which he or she can exchange for desired items.
B) contingency contracting- an individual models desired behaviour for the client.
C) observational learning- the therapist and client create a written agreement specifying the consequences for desirable and undesirable behaviours.
D) contingency contracting-an individual is rewarded for desired behaviour with such items as chips or play money, which he or she can exchange for desired items.