When You Are Walking Through a Zoo and You Enter

When you are walking through a zoo and you enter the "Africa Experience" exhibit,you would be very surprised to see a polar bear or a penguin,but probably not at all surprised to see an elephant or a rhinoceros.Why is that?

A) because of crosslinking of sensory experiences
B) because the opponent-process theory allows for only one "schema" of animal to occur at a time
C) because bottom-up processing will not allow you to accept an animal out of its place
D) because of a perceptual set about what you will see in that exhibit