Which of the following is an assumption on which the argument relies? A. Industrial pollution is the principal source of heavy metals in marine sediments. B. Harpacticoids are the only crustaceans that feed on microorganisms by ingesting sediment particles. C. Harpacticoids are more susceptible to poisoning by heavy metals than are other marine organisms. D. The microorganisms that harpacticoids feed on are not killed by pollutants that are harmless to harpacticoids. E. The microorganisms that harpacticoids feed on absorb heavy metals.