Though myopia, nearsightedness in one or both eyes, is believed to be a hereditary disorder, scientists propose that environmental factors such as stress and nutrition may also play a role in the progression of the disease. Adults who, as children, were diagnosed with mild cases of myopia and whose cases of myopia have remained relatively mild report that they have always refrained from reading in dim light; thus, a child diagnosed with a mild case of myopia can increase the likelihood that his or her condition will not become significantly more severe by refraining from reading in dim light.

A flaw in the argument above is that it


(A) provides reasons for the validity of its conclusion that presuppose the validity of that conclusion

(B) proceeds as though a condition that by itself is enough to guarantee a certain result must necessarily be present for that result to occur

(C) assumes without evidence that a behavior and a state which occur simultaneously share an underlying cause

(D) concludes that a practice causes a phenomenon when, at best, only an association between the two has been established


(E) fails to acknowledge that the stability of a condition experienced by a subgroup of individuals within a greater population will not necessarily be shared by the entire population

D