Naturalist: For several years, coyote have had a robust population throughout the Susquehanna National Forest. Over the past seven years, the Canic Chemical Corporation in nearby Harrisville has been releasing low levels of bromide compounds into the air and groundwater. Some of these compounds, in sufficient concentrations, are suspected of compromising the immune systems of young coyote. A recent study over the entire forest established that 30% of young coyote did not survive their first year of life. Clearly, the bromide compounds released by Canic pose a direct threat to the well-being of coyote in the forest. The answer to which of the following would be most useful for evaluating the naturalist's reasoning? ['How many of the natural springs in the forest derive from groundwater that flows in the vicinity of Harrisville?', 'What naturally available nutrients would strengthen the immune system of young coyote against any effects of these bromide compounds?', 'What percentage of healthy coyote survive to adulthood in the wild?', 'Have significant levels of these bromide compounds been measured in the blood of other mammals in the forest?']