一道令人头大的逻辑题！

jameswei0605

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.

 

Which of the following, if true, casts most doubt on the conclusion?

 

1. 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.
2. 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.
3. 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.
4. The sound of a boat engine generally travels much further under water than it does through the air.
5. 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.

答案选E 为什么呢？请指点！！谢谢

gonghao

E是说在各种转速下，只要是背景音正常，这个动物总是听不清的。

所以这个方法并非是因为这个动物听不清所以失败，而是因为即使不降低速度，背景音一来，这个动物总是分辨不了。所以如果有这样的情况，速度还是低点好

zijing4546

题干想拿轮船发出的声音说事,E选项告诉你,声音不是问题