单选题

　　[阅读选择]In a special report on cancer and blacks， the organization said blacks are usually diagnosed with cancer later than whites， and they are more likely to die of the disease.

　　Which may NOT be a reason for higher cancer death rates among US blacks？

　　A.Unequal access to medical care.

　　B.Greater probability of having other diseases.

　　C.Differences in the biology of the cancer.

　　D.Early diagnosis.