GWD1-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
为什么不能选C呢？不是前面说人类对其的影响，后面说自然对这种鱼的影响吗？？
GWD1-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
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
求问为什么选B而不是D呢？不是文章里也有说会导致基因的减少吗？ | 
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发表于 2011-3-1 13:03:48
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