About eight months ago, 14-year-old Shelley went on a drastic weight-loss diet that caused her to drop from 110 to 80 pounds. Although she is now dangerously underweight and undernourished, she continues to think she looks fat. Her frustratedfather recently forced her to eat a peanut butter sandwich, but Shelley immediately went to the bathroom and threw it all up. Shelley most clearly suffers from

A) hypermetabolism.
B) excess PYY.
C) an abnormally low set point.
D) bulimia nervosa.
E) anorexia nervosa.