A recent study has provided clues to predator-prey dynamics in the late Pleistocene era.Researchers compared the number of tooth fractures in present-day carnivores with tooth fracturesin carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Breatar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher thanthose in the present-day species.
In considering possible explanations for this finding, the researchers dismissed demographic biasbecause older individuals were not overrepresented in the fossil samples. They rejectedpreservational bias because a total absence of breakage in two extinct species demonstrated thatthe fractures were not the result of abrasion within the pits. They ruled out local bias becausebreakage data obtained from other Pleistocene sites were similar to the La Brea data. Theexplanation they consider most plausible is behavioral differences between extinct and present-daycarnivores-in particular, more contact between the teeth of predators and the bones of prey due tomore thorough consumption of carcasses by the extinct species. Such thorough carcassconsumption implies to the researchers either that prey availability was low, at least seasonally, orthat there was intense competition over kills and a high rate of carcass theft due to relatively highpredator densities.
The primary purpose of the passage is to______

A. present several explanations for a well-known fact
B. suggest alternative method of resolving a debate
C. argue in favor of a controversial theory
D. question the methodology used in a study
E. discuss the implications of a research finding