All of the Following Statements About Sickle-Cell Anemia Are Correct

All of the following statements about sickle-cell anemia are correct except:

A) it came to the attention of geneticists when it was observed that most North Americans who suffer from it are of African ancestry.
B) it was traced to abnormalities in populations that live in a clearly defined belt across tropical Central Africa.
C) it is notable in areas where high rates of deadly form of malaria is common.
D) because it is a disease of adaptation,it can never be brought under control or eradicated.
E) heterozygous individuals suffer few negative consequences except under stress or low oxygen.