A therapist is helping a client get rid of his fear of spiders. First, the therapist has the client think of spiders while using breathing techniques to calm himself. The therapist then has the client look at a picture of a spider and use the breathing techniques again. By the end of the therapy, the client is no longer afraid of spiders. The therapist has been using a technique created by B. F. Skinner that is called:
a. punishment.
b. shaping.
c. discrimination.
d. higher order conditioning.