According to the passage, biologists have suggested which of the following about snowshoe hare population fluctuations? A. Their regularity is due to the persistent threat of malnourishment that young hares face. B. They are similar in length to those of other species of hare. C. Their synchrony can be partly explained by the ability of predators to change the areas in which they hunt. D. Their variation from region to region is partly due to regional differences in the availability of alternate prey for predators. E. Their regularity is due to the constant availability of the food sources hares rely on.