Which of the following describes research that is most clearly analogous to the testing done by GRIP scientists? A. Scientists studying the formation of the Sahara desert measure the rate of topsoil erosion in the region B. Scientists seeking to determine the age of a particular fossil measure the percentage of its carbon atoms that have decayed C. Scientists researching vision in flies measure and compare the amounts of vitamin A found in the retinas of several fly species. D. Scientists investigating the development of life on Earth measure and compare the amount of oxygen used by various organisms along the evolutionary scale. E. Scientists plotting the fluctuations in rainfall in the early rain forests measure the presence of certain gases trapped in tree rings of older trees.