Ricky was hiking in the woods when he heard a rustling noise in the leaves where he had just stepped. Ricky, who has never been harmed by a snake, instantly jumped forward a full two feet, fearing a snake might be near his foot. Psychologists would explain Ricky’s fear of snakes as a(n):

a. biological predisposition that may help Ricky survive.
b. example of spontaneous recovery of an old childhood fear.
c. sensible response based on Ricky’s ability to generalize.
d. example of behaviorism.