下面进行GMAT考试重点试题整理，希望考生充分利用文中所列内容，提高备考效率。
GWD-1-Q9:
The primary purpose of the passage is to
A. argue against a conventional explanation for the extinction of certain salmon populations and suggest an alternative
B. correct a common misunderstanding about the behavior of salmon in response to environmental degradation caused by human activity
C. compare the effects of human activity on salmon populations with the effects of natural disturbances on salmon populations
D. differentiate the particular effects of various human activities on salmon habitats
E. describe how environmental degradation can cause changes in salmon populations that extend beyond a numerical reduction
The numerical effect is obvious: there are fewer salmon in degraded regions than in pristine ones; however, habitat loss also has the potential to reduce genetic diversity. Indeed, most analysts believe that some kind of environmental degradation underlies the demise of many extinct salmon populations.
注意extend beyond和主题句中的however, reduce genetic diversity
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*GWD-1-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迷惑选项
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定位36-40
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.
Should=if
E. the extinction of the salmon populations that spawn in polluted streams is accelerated
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GWD-1-Q11:
According to the passage, human activity has had which of the following effects on salmon populations?
A. An increase in the size of salmon populations in some previously polluted rivers
B. A decline in the number of salmon in some rivers定位第一段Line 1-7
C. A decrease in the number straying salmon in some rivers
D. A decrease in the gene flow between salmon populations that spawn in polluted streams and populations that spawn in pristine streams
E. A decline in the vulnerability of some salmon populations to the effects of naturally occurring habitat destruction
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*GWD-1-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 但是有一点，文中说的是影响genetic flow而这里说的是genetic structure
C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured无关，没有提到要衡量，文中强调的是人类活动对洄游的影响
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
以上是对GMAT考试重点试题整理的介绍，希望对考生有所启发，能够加快备考进度，取得GMAT高分。
