Which of the Following Involves the Development of a Phobia

Which of the following involves the development of a phobia through operant conditioning?

A) The person has a predisposition to develop a phobia about objects or situations that represented a threat to survival in our evolutionary past.
B) As a result of a stimulus being associated with an unpleasant event, this previously neutral stimulus now becomes a conditioned stimulus and elicits a fear response.
C) The person learns to fear a particular object or situation by observing another person reacting fearfully to it.
D) Avoiding the feared object or situation is negatively reinforcing, so the person is more likely to avoid the feared object or situation again in the future.