People with eating disorders is psychological because

because people have a poor perception of their image.

Explanation:

People who develop an eating disorder such as anorexia and bulimia are people who have low self-esteem. They look in a mirror and do not like what they see of themselves, so they resort to extreme eating behaviors to achieve what they call "ideal weight."

out of the choices i'd say d the ability to set goals, mainly because to desire to continue you need motivation but it isn't motivation in that part, but setting goals means you have an endgame and you want to reach it which sums up motivation.