Susan Is 16 Years Old and She Is Afraid of Gaining

Susan is 16 years old and she is afraid of gaining weight and getting fat. Susan is very dissatisfied with her body and she often tries to lose weight through fad diets and exercise. It would be difficult to determine her diagnosis because

A) it is hard to determine whether she meets the DSM-5 criterion for restriction of energy intake leading to low body weight.
B) Susan could have any one of a number of eating disorders.
C) Susan is still too young to have an eating disorder.
D) Susan's symptoms are not extreme.
E) it is difficult to determine whether she is successful at losing weight.