请教GWD-29-Q9

雨潇

我觉得这道题让人混淆的是哪个是结论——是最后一句这个方法不行还是倒数第二句M在船满行的时候更听不到低调声音。通过研究选项发现结论是后者。

削弱题要找结论的茬。看选项E，M根本对船音没反应，很显然结论不成立。

-- by 会员 sugaryun (2010/8/1 3:17:58)

结论不应该是后者吧，还是应该是最后一句话，E选项是质疑了M在船速度快的时候听不到低调的声音，原文含了一个隐含的意思就是低速的时候与高速的时候发出的声音相比，不容易被M听到，E是说明低速的时候与高速的时候发出的声音M都听不到，否定了推出结论的理由，也就否定了结论。

langrenly

我的第一感觉也是选b，
感觉b是质疑了结论，d是质疑了推导过程。

-- by 会员 yongjun (2010/8/1 0:12:10)

我认为这道题的关键点在于结论的may，如果结论是must be或者没有may，那么B其实更符合要求，但是结论说这个方法”可能“会变坏，那么不知道影响食物来源和听不见哪个效果更明显，自然没法断定可不可能。而E项，根本就否定了听不见的作用，自然就不可能了。

gete999

个人感觉B选项增加了一个变量，就是说（1）船减速是有利于生物的减少碰撞 （2）船减速是不利于生物觅食的
一正一反，不好衡量。

incredible1988

worse rather than better 取非的话是更好或是没影响

gedn01

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

over normal background noise就是正常情况下,M不能分辨出the sounds

jaze

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?

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.

个人感觉B选项增加了一个变量，就是说（1）船减速是有利于生物的减少碰撞 （2）船减速是不利于生物觅食的
一正一反，不好衡量。

-- by 会员 gete999 (2010/9/23 21:03:49)

我觉着B是一个无关选项， B中虽然说了船减速有利于water hyacinth的生长， 但是论据中并没有说如果船不减速的话 water hyacinth的生长情况怎么样， 如果已经满足 M 觅食的需要了， 那么船减不减速对M都没有影响。虽然减速可以使water hyacinth长的更好，可惜无用

ceciliazlh

B是他因削弱，E是直接削弱，显然E更好。

zongheimun

B项说法加入了其他因素（即开慢船有利于保护海牛的食物），但如果原题中的原因依旧成立（即开慢船有可能使海牛听不见发动机而造成更多事故死亡），两个因素加在一起，结果不一定是变好还是变坏。所以B项不能推出开慢船不会变差的结论，有可能保护了食物，但却出现了更多事故造成死亡，那么慢船还是worse的。
而E项削弱了题目中的前提，即开慢船还是快船海牛都听不到发动机。削弱了慢船会造成更多死亡的条件。

cynthia628

B相对E于原文建立的联系没有那么直接。B没有涉及到sound，E涉及到了sound,在BE都可能削弱原文的情况下，E比B更好。

luckysw

小女子浅见。
选B
此题结论是Therefore, this approach may in fact make things worse rather than better. 要反驳就要说this approach是好的，不会make things worse. this approach是指boat traffic in manatee-populated waters is being required to maintain very low speeds，也就是船要慢开。我们要选的答案应该是说船应该慢开。
A 说选地方的，无关
B 正答。M这动物的食物是h，这个h需要安静，快船会打扰甚至破坏h, 那h都破坏了，m就饿死了呀，所以要开慢船。
C 增长及现状，无关
D 这个很混淆视听，但是还是错的。因为题目中说M unable to hear low-pitched sounds，与声音传的远近无关的。
E M接触各种速度后，我们发现他们不能分辨出声音和背景，那么快船，慢船就无所谓了。

请各位大师评鉴。