Biologists have noted reproductive abnormalities in fish that are immediately downstream of paper mills. One possilbe cause is dioxin, which paper mills release daily and which can alter the concentration of hormones in fish. However, dioxin is unlikely to be the cause,since the fish recover normal hormone concentrations relatively quickly during occasional mill shutdowns and dioxin decomposes very slowly in the environment. Which one the following statements, if true, most seriously weaken the argument? A. some of the studies that show that fish recover quickly during shutdowns were funded by paper manufacurers. B. the rate at which dioxin decomposes varies depending on the conditions to which it is exposed. C. normal river currents carry the dioxin present in the river far downstream in a few hours. D.some of the fish did not recover rapidly from the physiological changes that were induced by the changes in hormone concentrations. E.the connection between hormone concentrations and reproductive abnormalities is not thoroughly understood. 请问,正确答案是什么?每错误选项是如何错的?本题的设计原理是什么? |