I will use the system of elimination to answer your question.
A - this is incorrect, because there are always variations in the understanding of something based on culture and nation
B - this is also incorrect, as there are a lot of cases of anorexia nervosa in Asian culture as well
D - this is incorrect, because anorexia nervosa is quite common in the Western culture
This leaves us with C. anorexia nervosa appears in Asian populations with the greatest amount of western influence, which should be the correct answer.