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In polluted environments, dolphins gradually accumulate toxins in their body fat, and the larger the dolphin the more accumulated toxins it can tolerate. Nearly 80 percent of the toxins a female dolphin has accumulated pass into the fat-rich milk her nursing calf ingests. Therefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida's Gulf Coast is probably the result of their being poisoned by their mother's milk.
Which of the following, if true, most strengthens the argument?
A. The survival rate of firstborn dolphin calves in the area along Florida's Gulf Coast is highest for those whose mothers were killed before they were weaned.
B. The rate at which adult dolphins living in the waters along Florida's Gulf Coast accumulate toxins is no higher than that of adult dolphins in comparably polluted waters elsewhere.
C. Among dolphin calves born in the area along Florida's Gulf Coast, the mortality rate is highest among those with living siblings.
D. As dolphins age, they accumulate toxins from the environment more slowly than when they were young.
E. Dolphins, other marine mammals, have a higher proportion of body fat than do most land mammals.
Reasoning
Given the facts stated, what would make the dolphin calf deaths more likely to have resulted from toxins in their mother’s milk? The dolphins live in a polluted environment. Therefore, the mother dolphins are accumulating toxins in their body fat. Most of the toxins in a mother dolphin pass through her milk into her nursing calf. Since dolphin calves are much smaller than their mothers, the calves are especially vulnerable to the toxins. The high mortality rate among the calves is more likely to have resulted from the toxins in the milk if calves who drink more milk have been more likely to die.
A. Correct. Calves whose mothers died before weaning would have drunk less toxic milk than other calves did, on average.
怎么也看不出A正确在哪儿啊，那些还没断奶的幼崽的死亡率高还可能是因为没奶吃呢啊？
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发表于 2014-3-25 10:24:09
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