1.         GWD-27-Q35

In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin 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?

1. 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.

2. 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.

3. Among dolphin calves born in the area along Florida’s Gulf Coast, the mortality rate is highest among those with living siblings.

4. As dolphins age, they accumulate toxins from the environment more slowly than when they were young.                                              

E. Dolphins, like other marine mammals, have a higher proportion of body fat than do most land mammals.       

答案是A,   可是我一点思路也没有,谁能帮我解释一下A选项,并给一个推理关系呀   先谢     

有毒的母乳--导致area along Florida’s Gulf Coast 幼仔的死亡率高

问加强。

A：在firstborn dolphin calves in the area along Florida’s Gulf Coast中， 母亲在其断奶前就死亡的dolphin calves 存活率最高。

这些存活率高的dolphin calves 和别的dolphin calves 相比，区别在于母亲是否在其断奶前就死亡。也就是说，dolphin calves 的存活率高低和其喂养母乳时间长短，多少有关

我是这么理解的。。。望NN们来指正~

題目結論:their mother’s poisoned milk-->high mortality rate among dolphin calves

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.

()內文字為選項內文
A , Strengthen: no poisoned milk (their mothers were killed before they were weaned)--> no high mortality rate among dolphin calves (survival rate is the highest)