GWD-29-9

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.

    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

答案选E,我觉得应该为B, 求教.

意思是不是说在实验中

不管船速如何manatees都是听不到的

所以开的慢一点并不会让情况变的更糟?

我觉得B对， 题目的结论是the aproach is worse rather than better. 削弱应该是反对此结论。 E里面是加强此结论啊。

B海牛的食物适于在静水中生长，船开得快会破坏其生长环境。 支持减慢船速， 结论是反对减慢船速， 所以是削弱啊。

以下是nettrinity 的发言：

我觉得B对， 题目的结论是the aproach is worse rather than better. 削弱应该是反对此结论。 E里面是加强此结论啊。

B海牛的食物适于在静水中生长，船开得快会破坏其生长环境。 支持减慢船速， 结论是反对减慢船速， 所以是削弱啊。

同意支持B，E为加强。

同意 E

在没有 E 的情况下，B 最好

问题要反对 "this approach may in fact make things worse", 也就是开慢船起了反作用，因为 Manatee 听不到船的声音，反而容易撞上 Manatee，那么我们就要证明开慢船能有作用，起码不会起反作用。E 正好说明了，开快开慢一样的，因为 Manatee 分不出来船的声音和背景声音。

在多想一点的话，开慢的话，即使撞上，后果也不会那么严重，对吧。