Trina attempts to overcome her fear of clowns by learning how to shift from a feeling of tension to one of calm and relaxation. Next, she is asked to imagine different situations, each more anxiety-provoking than the previous. She only proceeds to the next situation if she can maintain her feeling of relaxation. Trina's therapist is using __________ to remove her fear.
a. person-centered therapy
b. systematic desensitization
c. modeling
d. exposure therapy