Studies recently published in the Journal of the American Medical Asso

Studies recently published in the Journal of the American Medical Association say that despite the widespread belief to the contrary, girls are just as likely as boys to have the reading impairment dyslexia. The new studies examined 450 children over a four-year period, from kindergarten through third grade. The research teams found that fewer than half the students referred to them for reading problems actually had them; and although the schools identified four times as many boys as girls as being dyslexic, independent testing by the research teams revealed that the impairment appeared in both sexes with equal frequency. Yet, over the past decades, elaborate research programs have been set up to find the biological basis for the presumed gender difference in developing dyslexia.

Which of the following, if true, best explains the seeming contradiction outlined above between the new research and the conventional sex-linked view of dyslexia?
--On the basis of highlighted part we can say that earlier more boys were thought to have been suffering from dyslexia than were girls. So we can summarise the passage as following:
New theory: B=G
Old theory: B>G

(A) Many boys who have dyslexia are not identified as suffering any learning disability. -Out of scope. We are worried about reading abilities.
(B) Many girls who do not have any learning impairment are incorrectly identified as having dyslexia. -Out of scope. Same reason as in A.
(C) Earlier research was based entirely on subjects who were diagnosed by teachers as having reading problems. -Correct. The final sentence of the argument states that research programmes were set up to find biological basis for presumed gender difference. As per the argument we ought to find the option that helps us find the source of such pre-assumption.
(D) For years, the incidence of dyslexia has been underreported in school children of both genders. -If this option were true then older theory would have been wrong
(E) Learning disabilities are not likely to become evident until a child has reached the fourth grade. -Out of scope