12:BOver the last 150 years, large
stretches of salmon habitat have
been eliminated by human activity:
Line mining, livestock grazing, timber
(5) harvesting, and agriculture as well
as recreational and urban devel-
opment. The numerical effect is
obvious: there are fewer salmon
in degraded regions than in pris-
(10) tine ones; however, habitat loss
also has the potential to reduce
genetic diversity. This is most
evident in cases where it results
in the extinction of entire salmon
(15) populations. Indeed, most
analysts believe that some kind
of environmental degradation
underlies the demise of many
extinct salmon populations.
(20) Although some rivers have
been recolonized, the unique
genes of the original populations
have been lost.
Large-scale disturbances in
(25) one locale also have the potential
to alter the genetic structure of
populations in neighboring areas,
even if those areas have pristine
habitats. Why? Although the
(30) homing instinct of salmon to their
natal stream is strong, a fraction
of the fish returning from the sea
(rarely more than 15 percent)
stray and spawn in nearby
(35) streams. Low levels of straying
are crucial, since the process
provides a source of novel
genes and a mechanism
by which a location can be
(40) repopulated should the fish
there disappear. Yet high rates
of straying can be problematic
because misdirected fish may
interbreed with the existing stock
(45) to such a degree that any local
adaptations that are present
become diluted. Straying
rates remain relatively low when
environmental conditions are
(50) stable, but can increase dramati-
cally when streams suffer severe
disturbance. The 1980 volcanic
eruption of Mount Saint Helens,
for example, sent mud and debris
(55) into several tributaries of the
Columbia River. For the next
couple of years, steelhead trout
(a species included among the
salmonids) returning from the
(60) sea to spawn were forced to
find alternative streams. As
a consequence, their rates of
straying, initially 16 percent,
rose to more than 40 percent
(65) overall.
Although no one has quantified
changes in the rate of straying
as a result of the disturbances
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the Mount Saint
Helens eruption. Such a dra-
(75) matic increase in straying from
damaged areas to more pristine
streams results in substantial
gene flow, which can in turn lower
the overall fitness of subsequent
generations.
Q10:
It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
A. pristine streams that are near polluted streams become polluted themselves
B. the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
C. the number of salmon in pristine habitats decreases relative to the number in polluted streams
D. an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
E. the extinction of the salmon populations that spawn in polluted streams is accelerated
Q12:
The author mentions the “aftermath of the Mount Saint Helens eruption” (lines 73-74) most likely in order to
A. provide an example of the process that allows the repopulation of rivers whose indigenous salmon population has become extinct
B. indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
D. show how salmons’ homing instinct can be impaired as a result of severe environmental degradation of their natal streams
E. show why straying rates in salmon populations remain generally low except when spawning streams suffer severe environmental disturbance
Q10，key is D，what's wrong with B?
Q12, the key is C, what's wrong with B?
Thanks for your patience to plough through this article.
are crucial, since the process
provides a source of novel
genes and a mechanism
by which a location can be
(40) repopulated should the fish
there disappear.
You may read the above sentence again, and understand the true meaning of "repopulated"
12:
B. indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
the text does not mention that disturbance can influence the genetic structure. only genetic flow can be affected.
To be discussed...
Weiyu, thanks. Yet I have some different opinion.
12, "measured" in C is wrong. The article doesn't talk about anything as to measuring something. Besides, " Large-scale disturbances in (25) one locale also have the potential to alter the genetic structure of populations in neighboring areas," mentioned this "genetic structure". The 2nd and 3rd paragraph actually are engaged in the impact that the disturbance in one locale has on another locale, so "indicate the extent..." is correct.
wanting more remarks....
For Q12: It hard to choose between B &C.
However, for item B the "Mount Saint Helens eruption" is irrelevant to the "by human activity" mentioned in choose B, although the eruption did have some effects on the salmon.
I prefer C. the eruption did provide us a reference for identify the effects of the human activity, although the reference by eruption is not by human activity.
What do you think, Tianwan?
Although no one has quantified
changes in the rate of straying
as a result of the disturbances
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the Mount Saint
Helens eruption.
12, Thanks, opeman. Yet I still hold my standpoint in that "no one has quantified changes" means no measuring is involved. So C is wrong.
And "aftermath of MSH eruption" is relative "disturbance of salmon habitat by human activity", so B should be OK
10, D is wrong because it mentions that "the recovered stream could be recolonized by new salmon populations".
In the stem of the question, the "occasional failure" opposes to "high rate". "high rate" means "diluted", so "occasional failure" should mean "without dilution".
Q12 I think C is better, althoughI have some reservation to the word "standard" there.
In paragraph 2 (P2) where effects of MSH eruption is discussed, the passage does not discuss any "disturbance of salmon habitat by human activity". The passage compares the effects of human activity with that of MSH eruption only in P3. So, although we can say that in P2, the author gives a reference (effects of MSH eruption), and later in P3 the author compares the effects of human activity with that reference, it's too far-stretched to say that mentioning of MSH itself indicates the effects of human activity.
12, Thanks, opeman. Yet I still hold my standpoint in that "no one has quantified changes" means no measuring is involved. So C is wrong.
And "aftermath of MSH eruption" is relative "disturbance of salmon habitat by human activity", so B should be OK
我的理解是：measure并不意味着定量，而是有 evaluation（评估）的意思。正是因为no one has quantified changes，所以，The 1980 volcanic eruption of
我的理解是：measure并不意味着定量，而是有 evaluation（评估）的意思。正是因为no one has quantified changes，所以，The 1980 volcanic eruption of
10、同意D。这题应该定位于原文的35-41行：Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. C选项是这句话的同意转换。
10、 Low levels of straying are crucial, since the process provides a source of novel (new)genes and a mechanism
by which a location can be repopulated (recolonized)should the fish there disappear.
同意10 D,12 C
我的选择: 10 12:B
I agree. Measure here means qualitative measurement.
For B, the genetic structure part is fine. However, "indicate the extent" seems to me a quantitative measurement, which is wrong. So C.
Q12 I think C is better, althoughI have some reservation to the word "standard" there.
In paragraph 2 (P2) where effects of MSH eruption is discussed, the passage does not discuss any "disturbance of salmon habitat by human activity".
Disgree, 文章第一段第一句就说了"Over the last 150 years, large stretches of salmon habitat have bben eliminated by human activity." 第二段第一句"Large_scale disturbances in one locale also have the potentail to alter the genetic structure of populations in neighboring areas" 第三段第一句很清楚地说，Although no one has quantified changes in the rate of straying as a result of the disturbances caused by human, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption."从这里可以推断出作者提到aftermath of the Mount Saint Helens eruption的目的是为了indicate the extent to which the disturbance of salmon habitat by human activity in one stream imght affect the genetiv structure of salmon populations ealsewhere.
BTW, 既然作者已经提到了no one has quantified chagnes in the rate of straying as a result of the disturbances caused by humans, 作者认为the result of the disturbances caued by human 同那个什么的eruptiong没有"质"上的区别。那么C答案中的provide a standard of comparision(量的对比)显然是和作者的观点想矛盾。
因此我选B
Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be
repopulated should the fish there disappear.
不好意思 问一下 这句要怎么翻译 should 的 作用 在这句是舍么?
应该跟10题 D an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
should 的用法一样
谢谢 !!
基本上當我一口氣讀完本文只認為惟B可成為正確答案, 大家不用想太複雜, 前一段舉出natural 大變動的effect, 而本段說雖無數据證明但可得出同結果 (= extend to which may affect), 因無數据, 故 stnadard comparision should be measure 僅為干擾答案, 尤其 should be measure, 本文無建議或需求他人來 measure故錯誤. 如捆惑者建議直接讀完這兩段. 千萬不要僅讀此段, 會被吳導. 附註我蠻相信我的閱讀能力的, 請相信正確答案為B
For Q12, C is wrong because this article does not intend to raise a standard to compare.
最后一段开头的意思是, 尽管没有人对人类所造成的危害做出过定量分析，但是相信其危害应该和圣海伦火山差不多.
Therefore, I think B is correct.
should = if [modal verb] formal use this when something might happen in the future but it is not likely
- We've planned everything very carefully, but should there be any problems, contact me immediately.
- Should you ever find yourself in Oxford, I'm sure Uncle Eric would be glad to see you.
哈 终于有人跟我问一样的问题
建议你 单字问题 查字典比较快
12 (C) provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
请问C中 which 指代什么?
谢谢
12 (C) provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
请问C中 which 指代什么?
谢谢
我觉得是standard
measure somebody/something against somebody/something phrasal verb
to judge someone or something by comparing them with another person or thing
Bridget did not think she had to measure herself against some ideal standard.
Measured against our budget last year, $2.7 million seems small.
第12题我选C。
文章第一段第一句就说了"Over the last 150 years, large stretches of salmon habitat have bben eliminated by human activity ...However, habitat loss also has the potential to reduce genetic diversity. This is most evident in cases where it results in the extinction of entire salmon populations. 我觉得这就是主题句，强调两种因素，人为及自然的对照。
再看第三段第一句，Although no one has quantified changes in the rate of straying as a result of the disturbances caused by human, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption."。 简而言之，既然人为因素的影响没有量化，也就没有理由来怀疑自然因素造成的后果有质的区别。
C选项中的standard of comparison 就是“ ... qualitatively different than what was seen in the aftermath ...” than 之后的东西。
请指教！
关于12题, 答案应该是B
B强调的是对基因genetic diversity的影响
D强调的是对数量population的影响
本文首先提到的是人类活动对数量的影响, 又提出对基因的影响. 从对基因的影响提出了stray这个概念. 之后解释stray, 解释人类活动如何影响stray, 但都是基于基因的多样性受影响而发起的讨论. 相反的, 对于population的讨论淡化了. 所有的讨论是围绕着基因多样性不足展开的, 而stray是直接原因.
因此, the aftermath of the Mount Saint Helens eruption 不可能跳到文章一开始去修饰强调已经不是文章中心的population.
请指正.关于12题, 答案应该是B
B强调的是对基因genetic diversity的影响
D强调的是对数量population的影响
本文首先提到的是人类活动对数量的影响, 又提出对基因的影响. 从对基因的影响提出了stray这个概念. 之后解释stray, 解释人类活动如何影响stray, 但都是基于基因的多样性受影响而发起的讨论. 相反的, 对于population的讨论淡化了. 所有的讨论是围绕着基因多样性不足展开的, 而stray是直接原因.
因此, the aftermath of the Mount Saint Helens eruption 不可能跳到文章一开始去修饰强调已经不是文章中心的population.
请指正.
我本来被你说服了
后来发现了B一个重要的陷阱："EXTEND"+"genetic structure"
自细读B，他说aftermath of the eruption提给了一个程度指标。
后面的修饰语加入一读，那个"程度指标"是在"genetic structure"方面
也就是说，eruption的结果造成了genetic structure改变到一个程度，那个程度是人类也可能造成的。
但63行仅指出eruption将鱼回流时的走失率由16%提高到40%>>至于对genetic structure的影响到什么程度，完全没有提到。
所以B非常狡猾，等于自行加入了 "影响走失率的程度" 就是 "影响genetic structure的程度" 的前提。>>ETS标准的跳跃思考的混淆选项!!!!!
C正确
要求nn来解决问题
我现在是觉得b也有道理是，c也有道理
我同意mike的说法
要作这道题应该看前文为什么会提到eruption。文中先说Straying rates remain relatively low when environmental conditions are stable, but can increase dramati- cally when streams suffer severe disturbance. 然后举的eruption的例子，它影响的应该是gene flow，而不是直接影响gene struture，这中间有一个gap。美国人的逻辑思维直接，所以我认为比较的应该是gene flow，而不是gene sturcture。
此外，comparation的确显示了这个例子的作用。should be measured也不一定非要是精确测量。可以是一个比较含糊的概念。
Q10 我有跟TIANWAN 一样的疑惑：答案B是不是原文high straying rate 的取非？
ETS在INFER类的题里最爱考取非了！
当然我也同意D，但第二遍做时发现B没法否掉？
谁能告诉我B哪里错了？
关于10：
原文：Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.
问题：It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
D. an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
完美的同意变换
如果说是取非的话：
原文：Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.
问题：It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
B. the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
我觉得local adaptations和the adaptations of salomn population，不是同一个概念。
还有就是题目中问到的mechanism，原文中已经将一件事情定义为mechanism，可是没有将某种适应能力的消失或者保存定义为一种mechanism
如果想到取非的话是不是太复杂了
关于12：
原文 Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption. Such a dramatic increase in straying from damaged areas to more pristine streams results in substantial gene flow, which can in turn lower the overall fitness of subsequent generations.
这一段是接上一段的，可以说是对上一段的总结，在讲人类的行为会对最终会引起多大的破坏，含有一种破坏程度意味。
B .indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
C讲一个衡量的标准，上文只提到eruption造成迷失率由14％上升到16％，而第三段开头说了Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans
关于10：
还有就是题目中问到的mechanism，原文中已经将一件事情定义为mechanism，可是没有将某种适应能力的消失或者保存定义为一种mechanism
偶被说服了，同意D。谢谢concong！！
关于12：
原文 Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption. Such a dramatic increase in straying from damaged areas to more pristine streams results in substantial gene flow, which can in turn lower the overall fitness of subsequent generations.
这一段是接上一段的，可以说是对上一段的总结，在讲人类的行为会对最终会引起多大的破坏，含有一种破坏程度意味。
B .indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
C讲一个衡量的标准，上文只提到eruption造成迷失率由14％上升到16％，而第三段开头说了Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans
12条我选B
为什么一定要纠缠与extent和standard of comparion呢，难道standard of compare就不一定是quantitative而不能是qualitative的么？
btw：是从16%到40％，当然这是个小问题。
i choice E according to the article
:Strayingrates remain relatively low when environmental conditions are stable, but can increase dramati- cally when streams suffer severe disturbance
could anyone be kind to tell me why Ｅ isn't correct ?
这题我看了前面的帖子还是很晕
请XDJM 解释一下好吗?
1) 作者在第二段提出 large- scale disturbance 之后, 再提到走失程度(low level of straying , high rate of straying高不高) , 走失程度跟 large- scale disturbance 是怎么连结起来得呢?
2) Low levels of straying are crucial, since the process provides a source of novel
genes and a mechanism by which a location can be repopulated should the fish
there disappear. Yet high rates of straying can be problematic…..
我想请教这里的 the process指的是什么呢?
还有这里的crucial是否跟后面的 problematic对应呢? 也就是说low 跟 high
走失率都有很大影响吗?
这题我看了前面的帖子还是很晕
请XDJM 解释一下好吗?
1) 作者在第二段提出 large- scale disturbance 之后, 再提到走失程度(low level of straying , high rate of straying高不高) , 走失程度跟 large- scale disturbance 是怎么连结起来得呢?
第二段的主题是Large-scale disturbances 会引起临近地区三文鱼基因结构的改变，the potential to alter the genetic structure of populations in neighboring areas 然后解释了原因。（注意这里提到了基因结构）
2) Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. 我想请教这里的 the process指的是什么呢? 还有这里的是否跟后面的 problematic对应呢? 也就是说low 跟 high 走失率都有很大影响吗?
本来三文鱼的少量迷路是好的，而且是某一种类重新回到临时被破坏的河流关键(crucial)的机制。（10题）process 指少量的迷路。
Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.
大量的迷路就有问题（problematic）了，因为迷路的三文鱼和原有河流三文鱼的杂交会干扰或稀释原有三文鱼的基因以至影响它们的生存能力。
后面圣海伦火山的例子是说明在环境改变的时候，确实会产生大量三文鱼迷路的情况。
第三段：尽管没有人能从数量上衡量来自人类的破坏对三文鱼迷路率的影响，但没有任何理由怀疑这种影响和我们已经看到的圣海伦火山的影响有质上的区别。从被破坏的地区迷路到未被破坏的地区的三文鱼大量增加（dramatic increase），造成严重的基因的流动（基因的变化），从而使下一代三文鱼总体的适应能力遭到破坏。
Q12，是针对第三段，作者为什么提到圣海伦火山的数据。
A. 提供一个例子。。。X
B. 指出人类对三文鱼栖息的某一河流的破坏可能影响到其他地方三文鱼的基因结构。
C.提出一个标准，据此可以衡量人类对三文鱼基因流动的影响。
D.表明回游的天性会被严重的环境破坏影响。X
E.表明为什么在没有环境破坏时三文鱼的迷路率是低的。 X
C中有一个明显的倾向是原文没有的：The impact should be measured against a standard of comparison. 作者一直强调的是这种影响的存在，没有提出任何进一步的行动或计划。
可惜我第一次也选了c.
同意philipzhou
12题到底有定论了吗?
我觉得B也有缺陷,就是楼上某位说的,这里举例定位到原文会发现其是在讨论对gene flow造成的影响 (line78)
而B是在说genetic structure..所以可能还是有GAP,但从意思上来说我倾向B.
Large-scale disturbances in one
locale also have the potential
to alter the
genetic structure of populations in neighboring areas,
i chose B
Large-scale disturbances in one
locale also have the potential
to alter the
genetic structure of populations in neighboring areas,
这道题真的很难在B C间做取舍，不过按照ets的出题思路，既然问的是第三段的内容就要到第三段去定位，这样三段首句是一个让步转折（刚好是ets很prefer，出题点密集的句型），该句两次提到了quantitive的字样，一次提到了rate，重点在后半句转折的内容，也就是对前半句的取非，而选项C提到了measure，standard均是对原文的关键词的改写，comparison是对引用原文句中的different than 的改写，因此，c更合适。而且in order to 题型是RC里相对较易拿分的题型，该类体出题思路十分明确，就是原文定位＋意思改写，这点看c都符合标准，不必做太深入的意思研究，考试时也根本没有时间
犯傻了，自己删掉自己的发言。
我的看法：选B
Although no one has quantified
changes in the rate of straying
as a result of the disturbances
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the
GWD-1-Q12:
The author mentions the “aftermath of the
returning from the
(60) sea to spawn were forced to
find alternative streams.另外，我认为对gene flow和genetic structure不要过份抠字眼，其实正是disturbance造成了gene flow，才会进一步影响genetic structure的，两者有着紧密的联系。
我认为12题应该选C，理由如下：
1.B)indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
the extent指the disturbance对genetic structure的影响程度，extent这个词本身就含有数量的意味，而第三段只说两者在质上的相同，因此用extent不对。而且，按照正常思维，既然要用MSH的例子来表明人类活动对基因结构的影响程度，那么在MSH的例子中作者一定会先说明volcanic eruption of MSH对基因结构的影响程度，可是第二段中volcanic eruption of MSH的影响在"As a consequence, their rates of straying, initially 16%, rose to more than 40% overall."这一句中体现，只说了对rates of straying的影响程度，并没有关于the extent to which volcanic eruption of MSH affect the genetic structure of salmon populations elsewhere的表述。因此判断不是indicate the extent ...
2.C)provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
这里的should be measured是说人类活动的影响应该如何来衡量，这和前面Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans(到目前为止还无法数量化)是不矛盾的。因为人类活动和自然现象造成的后果两者在本质上是相同的，不管人类活动不能使rates of straying从16%上升到40%这么多还是使rates of straying上升得更多，总之它一定是使rates of straying上升的，这就是它们的相同之处，也就是衡量the impact of human activity之比较标准，相当于一个在进行数量研究前就已经被公认的真理(理论上的)，如果在对人类活动进行数量研究之后得出的数据表明rates of straying从16%下降到了10%(for example)，那么根据之前确认的理论上的结论，这个数据应该是>16%，而不是<16%，所以10%这项数据一定是错误的。而且原文line71~72处的"different than"明显暗示是做对比了。
综上所述，答案应该是C
To be discussed ...
楼上是不是理解错了？
原文是在说人类的影响和自然环境的影响有质的区别，即他们带来的影响没有可比性，那么既然如此，列举火山对鲑鱼的影响又怎么可能暗示了人类的行为的影响程度呢？
困惑！ 好像BC都不对
there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the
there is no reason to suspect that 不就是说毋庸置疑。。。吗？ 怎么都理解反了？
我原来也选了B, 第三遍做这篇文章时，发现BC都不对。 只好选D, 也不觉得D有明显的错误
there is no reason to suspect that 不就是说毋庸置疑。。。吗？ 怎么都理解反了？
我原来也选了B, 第三遍做这篇文章时，发现BC都不对。 只好选D, 也不觉得D有明显的错误
你理解反了~~
there is no reason to suspect that+从句=there is no reason to think that+从句，意即从句的内容是错的。
Low levels of straying
are crucial, since the process
provides a source of novel
genes and a mechanism
by which a location can be
(40) repopulated should the fish
there disappear.
想请教一下这句话的阅读。尤其是那个should the fish there disappear...
mao se dun kai
wu hu ai zai!!!
这道题真的很难在B C间做取舍，不过按照ets的出题思路，既然问的是第三段的内容就要到第三段去定位，这样三段首句是一个让步转折（刚好是ets很prefer，出题点密集的句型），该句两次提到了quantitive的字样，一次提到了rate，重点在后半句转折的内容，也就是对前半句的取非，而选项C提到了measure，standard均是对原文的关键词的改写，comparison是对引用原文句中的different than 的改写，因此，c更合适。而且in order to 题型是RC里相对较易拿分的题型，该类体出题思路十分明确，就是原文定位＋意思改写，这点看c都符合标准，不必做太深入的意思研究，考试时也根本没有时间
我认为12题应该选C，理由如下：
1.B)indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere
the extent指the disturbance对genetic structure的影响程度，extent这个词本身就含有数量的意味，而第三段只说两者在质上的相同，因此用extent不对。而且，按照正常思维，既然要用MSH的例子来表明人类活动对基因结构的影响程度，那么在MSH的例子中作者一定会先说明volcanic eruption of MSH对基因结构的影响程度，可是第二段中volcanic eruption of MSH的影响在"As a consequence, their rates of straying, initially 16%, rose to more than 40% overall."这一句中体现，只说了对rates of straying的影响程度，并没有关于the extent to which volcanic eruption of MSH affect the genetic structure of salmon populations elsewhere的表述。因此判断不是indicate the extent ...
2.C)provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured
这里的should be measured是说人类活动的影响应该如何来衡量，这和前面Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans(到目前为止还无法数量化)是不矛盾的。因为人类活动和自然现象造成的后果两者在本质上是相同的，不管人类活动不能使rates of straying从16%上升到40%这么多还是使rates of straying上升得更多，总之它一定是使rates of straying上升的，这就是它们的相同之处，也就是衡量the impact of human activity之比较标准，相当于一个在进行数量研究前就已经被公认的真理(理论上的)，如果在对人类活动进行数量研究之后得出的数据表明rates of straying从16%下降到了10%(for example)，那么根据之前确认的理论上的结论，这个数据应该是>16%，而不是<16%，所以10%这项数据一定是错误的。而且原文line71~72处的"different than"明显暗示是做对比了。
综上所述，答案应该是B。
To be discussed ...
有道理。
还是选C吧，根据考试时间限制和ets的出题习惯，只有C说得过去。
修正一下
我认为这题定位三段首句不够，还要继续看完后面那句。其意思是说人类活动的影响和MSH的影响（后句表明是对gene flow的影响）在定性方面没有差别，所以这里提供了对人类活动影响的一个标准，就是MSH的结果－增大gene flow，所以C应该是正确答案。
答案为C.
Line66: Although no one has quantified changes in the rate of straying…..
quantified量化 表示一定会有影响, 但程度不知道
而B: indicate…. might affect … 不对
我选B.
C中的"should"实在和主题偏离太远了。
i would prefer B in Q12.
全篇在讲人类的行为对salmon的影响，最后一句话“in substantial gene flow, which can in turn lower the overall fitness of subsequent generations”其实就是对应B中的“affect the genetic structure”，因为只有影响了基因结构才会造成lower subsequent generations.
这道题实际上在做类比。C最大可疑之处就是standard.
我觉得选B,那个eruption最初出现在倒数第二段,其内容还是支持首句"Large-scale disturbances in one locale also have the potentialto alter the genetic structure ofpopulations in neighboring areas,even if those areas have pristine habitats."
至于最后又把"eruption "拿出来,有点呼应前面的感觉,也是为了文章紧凑,通观全文的话， 应该选B,如果只定位最后一段,恐怕就要出现理解上问题,因为最后一段还是要为本文中心服务的， 所以,应该选最靠近文章中心的选项
我觉得应该选C。
文章两次提到那个火山爆发，但是题目问的是后面那次的作用，这显然因该优先考虑第三段的内容。
从逻辑上讲，我认为第二段讲gs会受环境大改变而改变，然后举例火山爆发会造成gs改变。第三段讲人类活动本质上与火山爆发没有区别，实际上是想得出结论人类活动会造成gs改变。
而b说作者暗示人类活动对gs改变的程度。”会改变“与”改变程度“意思是不一样的。
而c中的should be measure正是作者想的出的结论：人类活动会造成gs改变。
不知大家是否同意。
我也是最开始看C觉得很别扭，看了大家的讨论，反复读了几次就发现ETS的意思了。
Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the
这是一个表转折的句子，翻译过来就是“虽然对于rate of straying的变化没有量化的分析，（但是）不能否定其影响将在质上与MSH不一样。”后半句的目的是要反对前半句，我们可以直接把前半句取非，就是说在数量上进行分析可行，想到这一点再去读C就不会觉得难受了。实际上，ETS把MSH作为一个衡量的标准，也就是C里所说的standard of comparation, 而且C的gene flow确实比B的genetic structure要来的好
欢迎讨论
哇哈哈 这题讨论的真……
无论这题选B或C，毫无疑问这是一个高难度题、高区分度题，遇上这种题，最后verbal也不会低，大家move on去研究别的啦！
我个人同意leisure的看法，既然考试时时间不够这么来研究，那么还是按照ETS对in order to的标准操作来做——定位+paraphrse——又快又好；就算错了又如何，至少时间没有费多少。
这道题目反复阅读看讨论后，觉得答案是C
关于B的extent题型可以参见og-48-284题，程度的比较应该是有difference存在
而这片文章最后一段一直在强调human activity和aftermath of the MSH eruption的作用同等性，显然a standard of comparison是答案的关键词。
B,C只见很难抉择。B中的extend确实有问题，稳中没有提到erption的extend,只谈到影响结果，没有谈到程度。可是C中的comparison也有问题，其实第3段不是为了表现对比，是为人类可能造成的后果作一个假设的后果，相当于比喻。并且C中的should语气太重，作者有倾向说人类活动改变基因，但是没有确定，只是可能而已。
Although no one has quantified
changes in the rate of straying
as a result of the disturbances
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the
这题肯定是B。genetic structure在第26行提到了，而且这句是主题句。
最后一段明说了disturbances caused by humans无法定量的衡量(no one has quantified changes...)，但是它在性质上可以和Mount Saint Helens eruption相比(no qualitatively different)。因此作者提Mount Saint就是把它和人类的行为类比，指出人类行为对主题句所说内容的影响有多大(the extent to which)。
C错在provide a standard for measurement。文中已经明说无法衡量，两者只是性质相同，Mount Saint Helens eruption并不是一个衡量标准(a standard of comparison)。
答案为C.
Line66: Although no one has quantified changes in the rate of straying…..
quantified量化 表示一定会有影响, 但程度不知道
而B: indicate…. might affect … 不对
就是因为no one has quantified changes...，才是might呀。
本文我个人认为较难，我做了好久，嗬嗬！
这道题我原来选了c，但是看了讨论觉得b好像好些！
首先是the Mount Saint
Helens eruption.的作用一定是给人类的破坏的影响作参照！因为前面说了no one has quantified
changes in the rate of straying
as a result of the disturbances
caused by humans
说明我们需要一个参照来quantified changes，所以选BC两项之一大家都是有共识的！
B说表明了程度，C说提供了标准！
先来说C吧，标准的意义在于，比如衡量某事物的影响，给出一个标准，当低于这个标准的我们认为它不构成影响，而高于他的才构成影响！
就像是考试，假如100分的卷子，60过，那么低于的就不及格，高于的就及格！再比如验货，有一个标准，通过了，就合格，反之，不合格！
因此标准的意义在于把事物的属性分为两个极端的方向！
这样一说就很明显了，the Mount Saint Helens eruption 显然并没有使人的影响极端话，不是说超过了他就有影响，不超过影响就忽略！
the Mount Saint Helens eruption 的作用在比较和衡量人类影响的程度！
比如说the Mount Saint Helens eruption 破坏了山川，田野，并造成了某种后果！而人类的行为也同样破坏了这些，且程度相仿，那么它也会造成相似程度的后果！通过此我们可以来quantified changes！
关于12题，看了大家讨论那么多，我想从另一个角度提出一些自己的看法，即怎样理解第三段的第一句话：
Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the
前半句although理解的和大家一样，转折的后半句结合在下一句话的意思应该是: 但是毋庸置疑的是（如果没有人类破坏的话）结果会有质的不同，即尽管MSH的爆发会导致salmon迷路的增长，但若是没有人类damage stream的话，salmon迷路也不会导致gene flow。
所以 disturbance of salmon habitat by human activity是根本原因，MSH的爆发帮助其实现了salmon的迷路，从而影响了genetic structure of salmon populations elsewhere, 因此选择B
10 B
12 C
10题我有很充分得理由, 等我考完了再和你们讨论. 请注意D 选项中should the stream recover 完全是一个全新的没有丝毫根据的附加条件, 在第二段中根本没有出现!
Large-scale disturbances in one
locale also have the potential
to alter the
genetic structure of populations in neighboring areas,
同意！
并且文章提到MSH只是一例，C说standard实在牵强
12题我支持B,文章是通过火山爆发的影响来暗示人类活动同样也会对鱼的基因产生影响。这里火山爆发只是作者用来说明人类活动影响时所借助的一个工具，哪里有什么把火山爆发作为标准来比较的意思啊？
所以我认为是B,即使在考试里遇到这道题目我也会坚持的我选择！
我选B，其中的elsewhere符合这两段讲的内容，鱼的迁移也会影响其他地方。
虽然我也看不太明白这篇文章，但是总觉得C中的standard文中并没有提到。文中提到quantity也只不过是一个让步，内容的重点还是在于后半句，强调确实产生了影响。
哪位牛人能把这篇文章的基本内容说一说吧，谢谢!
前面有两位说得对，就是这么回事。作者说那个ERUPTION就是举个极端的例子，他也可以说“那些改变总不是来自于外星人的创在吧。”之类的。
我选B，其中的elsewhere符合这两段讲的内容，鱼的迁移也会影响其他地方。
虽然我也看不太明白这篇文章，但是总觉得C中的standard文中并没有提到。文中提到quantity也只不过是一个让步，内容的重点还是在于后半句，强调确实产生了影响。
哪位牛人能把这篇文章的基本内容说一说吧，谢谢!
MM see this link
http://forum.chasedream.com/dispbbs.asp?BoardID=25&ID=109543
12题目C比B好
理由如下：
首先从细节来考虑，B和C可以说都不很严密。（B. indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere）the extent 是指数量还是质量呢？如果指质量那肯定是错误选项，因为这和66—69行（ Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans,）内容矛盾。当然C也有逻辑不严密的地方，比如standard也是文章中没有提及的。
所以我认为应该不管细节，专注文章总体结构，文章40行说“Yet high rates of straying can be problematic”，然后55行说“The 1980 volcanic eruption of Mount Saint Helens, for example, sent mud and debris into several tributaries of the Columbia River. ”然后“ For the next couple of years, steelhead trout returning from the sea to spawn were forced to find alternative streams. As a consequence, their rates of traying, initially 16 percent, rose to more than 40 percent overall.”最后就是讨论的中心“Although no one has quantified hanges in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption.”问题要问的是提及“aftermath of the Mount Saint Helens eruption” (lines 73-74) 的目的是什么，根据上面的文章结果可以看出：作者是想说明high rates of straying can be problematic，然后提出理由是“ the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere”，最后结论“Although no one has quantified hanges in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption.”其中作者在73—74行说明的MHS是结论的一部分，如果选B那等于是说得出结论的目的是为了阐明理由。
C只是一个合理的推断，当然着这是以不考虑细节为前提的，尽管推断的很多内容文章中没有提及。
第12题，看了所有的讨论，又重复看了N遍原文、题干和选项，最终，我认为是B是正确的，C不可能是正确答案.
Over the last 150 years, large
stretches of salmon habitat have
been eliminated by human activity:
Line mining, livestock grazing, timber 第一段：以人类活动使salmon habitat消失开头，列举人类活动对salmon population的影响：
(5) harvesting, and agriculture as well 1、数量减少， 2、(人类活动造成habitat loss，而hatbitat loss会）减少基因多样性。
as recreational and urban devel-
opment. The numerical effect is (注意，第2出现在however之后，是作者 强调和将说明的重点）之后均是顺接关系。
obvious: there are fewer salmon
in degraded regions than in pris-
(10) tine ones; however, habitat loss
also has the potential to reduce
genetic diversity. This is most
evident in cases where it results
in the extinction of entire salmon
(15) populations. Indeed, most
analysts believe that some kind
of environmental degradation
underlies the demise of many
extinct salmon populations.
(20) Although some rivers have 第一段最后一句，再次强调：虽然一些河流可以再度有鱼，但原来鱼群的独有的基因却已丢失
been recolonized, the unique 表明：鱼数量的减少并非无可挽回（can be recolonized）,而独有基因的丢失却无可挽回（have
genes of the original populations been lost）。注意：Although...,...句式的强调重心。
have been lost. 可见，文章讨论的重点将是人类活动对鱼群影响的第二条——对基因方面的影响。
Large-scale disturbances in 第二段提出更深一层的研究：一个地区被大规模扰乱（不仅会使当地的鱼群基因丢失）还会
(25) one locale also have the potential 改变邻近地区鱼群的基因结构。（继续说对基因的影响）并解释原因。
to alter the genetic structure of
populations in neighboring areas,
even if those areas have pristine
habitats. Why? Although the
(30) homing instinct of salmon to their
natal stream is strong, a fraction
of the fish returning from the sea
(rarely more than 15 percent)
stray and spawn in nearby
(35) streams. Low levels of straying 说明low level of straying很至关重要(会影响邻近区域的鱼群)，
are crucial, since the process 它提供：为邻近区域的鱼群提供新的基因组合的来源
provides a source of novel 还提供：如果原来的鱼群消失，一个区域的河流可被repopulate的机制。
genes and a mechanism
by which a location can be
(40) repopulated should the fish
there disappear.
Yet high rates
of straying can be problematic
because misdirected fish may
interbreed with the existing stock
(45) to such a degree that any local 注意：这里的Yet不仅起到转折和对比的作用（low与high比），还提出了新问题：
adaptations that are present high rates of straying将引发问题——misdirected fish会与邻近区域的鱼群大量杂交——
become diluted. 造成any local adaptations that are present become diluted.
Straying
rates remain relatively low when
environmental conditions are
(50) stable, but can increase dramati- 当河流被严重扰乱时，鱼的迷路就会激增——出现high rates of straying。
cally when streams suffer severe 例如：1980年的Mount Saint Helens火山爆发使哥伦比亚河的许多支流受污。这使rates of
disturbance. The 1980 volcanic straying从16％激增到40％，从大海回来的鱼群也被迫寻找其它河流产卵。（与
eruption of
for example, sent mud and debris
(55) into several tributaries of the
couple of years, steelhead trout
(a species included among the
salmonids) returning from the
(60) sea to spawn were forced to
find alternative streams. As
a consequence, their rates of
straying, initially 16 percent,
rose to more than 40 percent
(65) overall.
Although no one has quantified 尽管还没有人量化（由人类干扰导致的）rate of straying的变化，但没有理由怀疑：
changes in the rate of straying 结果会与Mout Saint Helens火山爆发的后果有质的不同。
as a result of the disturbances （也就是说，结果不会与Mout Saint Helens火山爆发的后果有质的不同）
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the
Helens eruption. Such a dra- 这种迷路的增加导致substantial gene flow, 进而降低后代的整体适应性。
(75) matic increase in straying from
damaged areas to more pristine
streams results in substantial
gene flow, which can in turn lower
the overall fitness of subsequent 这里的后代就是大量straying的鱼与existing stock杂交后的鱼，这些后代
generations. 丢失了straying鱼原有的local基因特性（any local adaptations that are present become diluted），
从而比straying鱼具有lower overall fitness.
注意：straying鱼和邻近区域的existing stock的基因都发生了变化，共同形成了subsequent generations.
Q12:
The author mentions the “aftermath of the
题干、选项与原文的对应，我已用相同的颜色进行标注，以帮助理解。
解12题的思路可由文中推理链得出：
Severe disturbance of salmon habitat by human activity in one stream→ high rates of straying from damaged areas to more pristine streams→ misdirected fish interbreed with the existing stock to such a degree that any local adaptation that are present become diluted→ substantial gene flow which can in turn lower the overall fitness of subsequent generations.
注意: 相应词汇的对应。
“aftermath of the Mount Saint Helens eruption”—— not be qualitatively different，所以是Severe disturbance of salmon habitat by human activity in one stream的一个具有代表性的实例。
注意体会原文中的such的含义：先说明以aftermath of the Mount Saint Helens eruption为代表的sever disturbance会引起dramatic increase in straying from damaged areas to more pristine streams. 再进而（在最后一句话中）总结性地重申了上面的推理链。
B为什么是正确答案应该很清楚了！！！
不好意思，不知怎的，颜色标注怎么没了，再把12题中题干、原文、选项的对应用不同颜色进行标注，以方便理解。
Although no one has quantified 尽管还没有人量化（由人类干扰导致的）rate of straying的变化，但没有理由怀疑：
changes in the rate of straying 结果会与Mout Saint Helens火山爆发的后果有质的不同。
as a result of the disturbances （也就是说，结果不会与Mout Saint Helens火山爆发的后果有质的不同）
caused by humans, there is no
(70) reason to suspect that the effect
would be qualitatively different
than what was seen in the
aftermath of the
Helens eruption. Such a dra- 这种迷路的增加导致substantial gene flow, 进而降低后代的整体适应性。
(75) matic increase in straying from
damaged areas to more pristine
streams results in substantial
gene flow, which can in turn lower
the overall fitness of subsequent 这里的后代就是大量straying的鱼与existing stock杂交后的鱼，这些后代
generations. 丢失了straying鱼原有的local基因特性（any local adaptations that are present become diluted），
从而比straying鱼具有lower overall fitness.
注意：straying鱼和邻近区域的existing stock的基因都发生了变化，共同形成了subsequent generations.
Q12:
The author mentions the “aftermath of the
题干、选项与原文的对应，我已用相同的颜色进行标注，以帮助理解。
此题尚无定论啊，都讨论两年了。
要等到2007年再来看啦~
就选B了，第一感觉很重要。不过要过分扣字眼了，阅读还是最好强调总体感觉比较好。
I hold for C, because C stress on "impact", while B focuses on "extent of disturbance". Obviously, the author give the eruption example to discuss what it brought about, not its activity(strong eruption or weak eruption). Please take time to taste the difference.
Waiting for comments from NN!
文章最后一段：人类的侵扰和大自然的改变对结论不会有太大出入。最后一句话：用大自然中火山爆发影响基因的例子来说明，人类的侵扰会造成相似的后果。所以答案C正确。
第10题
Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism
by which a location can be repopulated should the fish there disappear。
（D）an environmentally degraded stream could be recolonized by new salmon populations should the stream recover。
有谁解释一下这两句话，第一个SHOULD我明白表示IF，即原本鱼都消失了
那D中SHOULD如何解释，它后面跟的是RECOVER与DISAPPEAR正好相反，不会再是IF的意思吧？
Q10:
My answer: D
Look for info fr the text:
Low levels of straying
are crucial, since the process
provides a source of novel
genes and a mechanism
by which a location can be
(40) repopulated should the fish
there disappear.
这个题考试中出现过么？ETS也觉得题出的别扭不要了吧
Q.10 I believe B is the best answer. When the stray rate is high,
(41) Yet high rates
of straying can be problematic
because misdirected fish may
interbreed with the existing stock
(45) to such a degree that any local
adaptations that are present
become diluted. (means that low rate won't be diluted)
Yes, the degraded stream could be repopulated, but not RECOLONIZED by NEW population. When you use colonize, it means the subject is not from local, however, the salmon is come from local.
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