GRE Reading Comprehension: OG/PP2-GRE阅读OG/PP2 - VI31OM0V1DFFE757P

It can be inferred that the author of the passage mentions predators primarily in order to A. help explain why Martin's hypothesis is incorrect B. identify one effect of adding iron to iron-poor waters C. indicate how some carbon dioxide is converted to solid organic matter D. help account for differences in the density of phytoplankton between different regions of the ocean E. point out a factor that was not anticipated by the scientists who conducted the field tests mentioned in the passage