What Does the Relationship Between Genetic Traits and the Prevalence

What does the relationship between genetic traits and the prevalence of diseases such as malaria and smallpox illustrate?

A) the ways in which human biological diversity reflects adaptation to such environmental stresses as disease, diet, and climate
B) the shortcomings of research that focuses on environmental variability but ignores genetics
C) how despite some evidence to the contrary, some human races are better than others
D) how with technology, human biology is less important to human survival
E) the mechanisms of hominid evolution