Fred is afraid of spiders. He won't even watch a nature show on TV about them. When he sees a picture of a spider, he has a panic attack, but when he avoids looking at the image, his panic goes away. Fred's avoidance of spiders is being __________

a) extinguished, because he feels anxious after doing so.
b) recovered spontaneously, because he will never get better.
c) positively reinforced, because he is rewarded by his anxiety going down.
d) negatively reinforced, because he is rewarded by his anxiety going down.

d