The author refers to dolphins in the Gulf of Mexico in the last paragraph in order to A. refute the assertion that dolphins tend not to inhabit areas where P. brevis is common B. compare the effects of synthetic pollutants on these dolphins and on Atlantic coast dolphins C. cast doubt on the belief that P. brevis contributes substantially to dolphin die-offs D. illustrate the fact that dolphins in relatively pollution-free waters are healthier than dolphins in polluted waters E. provide evidence for the argument that P. brevis was probably responsible for the dolphins' deaths