[求助]GWD1-11(已经搜索了)

Q11:

According to the passage, human activity has had which of the following effects on salmon populations?

1. An increase in the size of salmon populations in some previously polluted rivers

2. A decline in the number of salmon in some rivers

3. A decrease in the number straying salmon in some rivers

4. A decrease in the gene flow between salmon populations that spawn in polluted streams and populations that spawn in pristine streams

5. A decline in the vulnerability of some salmon populations to the effects of naturally occurring habitat destruction

E 能否理解为 a decline in the vulnerability of (some salmon populations to the effects of naturally occurring habitat destruction) 受自然因素影响的生活环境的破坏对salmon数量的有所影响－这条理论的攻击性下降，也就是说人为因素对salmon的数量影响是主要的

不知道E选项这样理解是否正确？

当然我也如同答案B

答案选B，定位第一段的这句话：The numerical effect is obvious:  there are fewer salmon in degraded regions than in pristine ones

选项E的意思是自然环境的破坏对鲑鱼种群的影响在下降。但是这是臆测的，是无关选项，因为作者没有提到这一点，作者只是说了人为活动对鲑鱼的影响和自然环境自然变化的影响的不同。