The prevalence of a simian virus has been directly correlated with population density in gorillas. Recent fieldwork in the Republic of Dunaga, based on capturing gorillas and testing the gorillas for the virus, has shown that Morgania Plain gorillas are more than twice as likely to be infected than are the Koluga Mountain gorillas. Nevertheless, the population density of Koluga gorillas is significantly greater than that of Morgania gorillas.

Which of the following could best account for the discrepancy noted above?

A:During periods of little rainfall, Koluga gorillas sometimes wander down into the plains in search of food.

B:Dormant strains of the simian virus are often difficult to detect.

C:Because of the Morgania gorilla`s natural habitat and its less reclusive nature, researchers have tested a greater number of Morgania gorillas than Koluga gorillas.

D:Infected Koluga gorillas behave very aggressively and are more difficult to subdue for testing.

E:The Koluga and the Morgania both have similar markings on their backs but are classified as different subspecies.