​Irene eats large quantities of high-calorie foods at least three times a week when she is alone or nervous. After binging, she induces vomiting. She is constantly concerned about her appearance, although she is of normal weight. An appropriate diagnosis for irene is ____.
a. ​binge-eating disorder
b. ​overanxious disorder
c. ​anorexia nervosa
d. ​bulimia nervosa