People with bulimia have elevated ghrelin levels. Is this abnormality a likely cause of bulimia? And what is the evidence?

a. No. It is probably not a cause. The abnormality is common in the ethnic groups who are most likely to develop bulimia.

b. No. It is probably not a cause. As people recover from bulimia, their ghrelin level returns toward normal.

c. Yes. It is probably a cause. People who show high ghrelin early in life are likely to develop bulimia later.

d. Yes. It is probably a cause. Inducing high ghrelin in rats causes the rats to develop bulimia.