In polluted environments, dolphinsgradually accumulated toxins in their body fat, and the larger the dolphin, themore accumulated toxin it can tolerate. Nearly 80 percent of the toxins a female dolphin has accumulated passinto the fat-rich milk her nursing calf ingests.  Therefore, the unusually high mortality rateamong dolphin calves in the industrially contaminated waters along Florida’s Gulf

Which of the following, if true, moststrengthens the argument?

A.   The survival rate of firstborn dolphincalves in the area along Florida’s Gulf

B.   The rate at which adult dolphins living inthe waters along Florida’s Gulf

C.   Among dolphin calves born in the area along Florida’s Gulf

D.   As dolphins age, they accumulate toxins fromthe environment more slowly than when they were young.

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

答案选A，我个人在A和D之间徘徊。为什么D会错？海豚随着成长积累T的速度减少，不正说明小时候的积累是由于喝奶吗？