请教各位大牛指点！！！GWD逻辑一枚

zxppx

28: GWD-29-Q9
Manatees, aquatic mammals inhabiting Florida’s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats.  To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds.  Unfortunately, manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows.  Therefore, this approach may in fact make things worse rather than better.（就是说船开慢会使情况恶化）
Which of the following, if true, casts most doubt on the conclusion?（即船开得慢是有好处的）
A.    The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.
B.    Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.
C.    Over the last several decades, boat traffic in Florida’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.
D.    The sound of a boat engine generally travels much further under water than it does through the air.
E.    When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.
答案是选E，但是看参考GWD的解释时，答案是选B！迷糊了

baixuefei0524

E.发帖前先搜索一下

zxppx

为什么选E呢，E是说海牛不能区分不同的声音，那么即使船开慢了，也没法帮助它区分啊！

baixuefei0524

所以说这件事跟声音无关。但是开慢了可以减少撞上动物的几率

zxppx

明白了！感谢！