In Ivan Pavlov's original demonstration of classical conditioning, why is the food referred to as an unconditioned stimulus?

a. Because the food is something the animal had to learn that it wanted in all cases.
b. Because the animal knows he is going to get food whether he salivates or not, so salivation is not a "condition" of getting food.
c. Because lower animals do not have the capacity to decide what they will and will not respond to, so all stimuli for animals other than human beings are "unconditioned."
d. Because the food evokes the salivation response before any intentional learning has taken place.

Answer: D