Why does the author provide the information that "the subpopulations of most species are separated from each other by some measurable distance"? A. To indicate how scientists are able to determine whether subpopulations of a species are allopathic. B. To define what it means for a group of animals or plants to be a subpopulation. C. To suggest that allopathic speciation is not the only route to speciation. D. To help explain why allopatric speciation is a common way for new species to come about.