求这道gwd逻辑试题的解释 WHY???

hsuehM

   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.

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.

这个逻辑试题为什么选E,请NN们指点.

atc

反驳：this approach may in fact make things worse rather than better。那最直接的就是那动物是对声音不敏感。暗含的意思就是说通过控制船的速度不能解决实质问题，不管船速快慢，那东西都会撞上船！MM，那你想想什么方法可以解决现在的问题呢？

hsuehM

...oh,thanks ,atc

就是速度使声音大小怎么变,情况和原来还是一样的,只有减少船的数量,Manatees的情况才会好转~~~