As a Serious Dancer, Petra Watches What She Eats

As a serious dancer, Petra watches what she eats. She knows that she is underweight, but fears that if she starts eating more, she will get fat. In addition to a preoccupation with food, she has also stopped menstruating. Petra's behaviors suggest that she might be suffering from __________.

A) anorexia nervosa
B) bulimia nervosa
C) compulsive exercise
D) phobic disorder