According to the passage, Hargrave and Geen did which of the following in their experiments? A. They compared the grazing rates of individual zooplankton species in the laboratory with the natural grazing rates of these species. B. The hypothesized about the population density of grazers in natural habitats by using data concerning the population density of grazers in the laboratory. C. They estimated the community grazing rates of zooplankton in the laboratory by using data concerning the natural community grazing rates of zooplankton. D. They estimated the natural community grazing rates of zooplankton by using data concerning the known population density of phytoplankton. E. They estimated the natural community grazing rates of zooplankton by using laboratory data concerning the grazing rates of individual zooplankton species.