GRE Reading Comprehension: ETS-GRE阅读ETS - OJ6442B351PM65_87

It can be inferred from the passage that the "first theories" of grazer control mentioned in the first paragraph would have been more convincing if researchers had been able to A. observe high phytoplankton numbers under natural lake conditions B. discover negative correlations between algae and zooplankton numbers from their field research C. understand the central importance of environmental factors in controlling the growth rates of phytoplankton D. make verifiable correlations of cause and effect between zooplankton and phytoplankton numbers E. invent laboratory techniques that would have allowed them to bypass their field research concerning grazer control